JPS63162225A - Manufacture of long timing belt - Google Patents

Abstract

PURPOSE:To produce continuously a timing belt having uniform thickness and excellent quality, while removing internal residual shrinkage stress by a method in which the flat thermoplastic sheet in which a tension resisting member is buried, is separately molded, and an elastomer molded object molding a sheet and a belt compression part in a softened state, in pressurized and heat-welded by a press roll. CONSTITUTION:While heating an elastomer by a heating lip movable up and down provided at a nozzle N so as not to cure the surface of the elastomer having been poured in a cavity C, the elastomer is pressurized, whereby the viscosity of the elastomer-surface is lowered into softened state, and simultaneously its surface is smoothed and is brought in a state suitable for heat welding. the molding material used here is mainly thermoplastic urethane. On the other hand, the sheet 6 of the thermoplastic elastomer having been cured in which a tension resisting rope 1 is buried at a prescribed position, is inserted into between a toothed mold M and a press roll by may of a press roll at a constant tension. A belt molded object is molded by heat- welding, pressurizing at a constant pressure so as to obtain prescribed thickness by a thickness adjustable rider roll T, while bringing the elastomer sheet to be integral with the belt compression part 4 at softened state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a manufacturing method for continuously molding a long timing belt with ends made of thermoplastic resin.

(Prior technology) Timing belts (toothed belts) are a periodic transmission system that transmits rotation without slipping, so timing belts made of rubber or polyurethane are widely used as power transmission belts for general industry, precision machinery, etc. However, the polyurethane belt is usually made by placing a cylindrical inner diameter of a predetermined size wrapped with a tensile material lobe into an outer mold, and injecting liquid elastomer (urethane) into the gap between the inner diameter and the outer mold. After curing,
A method has been adopted in which the resulting wide belt molded body is cut into a predetermined width, but this method only yields an endless belt of a predetermined size and requires a large number of molds to obtain belts of different sizes. In addition, there was a problem in that the above-mentioned molding method could not be used to obtain a long timing belt.

In order to solve these problems, recently the special public
As disclosed in Japanese Patent No. 5701, there is a method of manufacturing a long timing belt by continuously extruding a thermoplastic resin or a thermoplastic elastomer using an extrusion molding machine.

(Problem to be solved by the invention) However, in the above manufacturing method, the space between the extruder nozzle and the cavity is sealed, so the molded and hardened product under pressure in the cavity has shrinkage stress. This remains as internal residual stress, and when the belt is driven for a long period of time, there are problems such as early cracking, which have negative effects on the belt life.

The present invention focused on this problem, and as a result of intensive research, a thermoplastic elastomer sheet containing a tensile material that constitutes the belt tension section is separately formed, and the sheet and the thermoplastic elastomer in a softened state in the cavity are connected to each other. The purpose is to eliminate shrinkage stress and continuously manufacture timing belts with uniform thickness and good quality by heat-sealing them.

(Means for Solving the Problems) That is, the present invention is characterized by forming a cavity between a rotary toothed mold having flanges on both sides and a nozzle of an extruder; The molten thermoplastic elastomer is injected and filled through a nozzle, and as the mold rotates, the cavity to be injected is moved in the rotational direction to continuously inject the elastomer into the cavity.Then, the heating lip attached to the nozzle is used to fill the cavity. The elastomer surface viscosity within the tee is reduced to a softened state, and the tensile material is embedded in a predetermined position via a presser roll that is disposed close to the front of the extruder so as to be able to roll with the mold. A plastic elastomer sheet is inserted between a toothed mold and a presser roll under constant tension, and heat-sealed to the softened compressed portion to a predetermined thickness while being pressed by a presser roll, and then as the toothed mold rotates. The purpose is to continuously form a toothed belt molded product by cooling and hardening.

(Example) Hereinafter, a method and apparatus for manufacturing a long timing belt according to the present invention will be described based on the drawings.

FIG. 1 is a schematic side view showing the manufacturing apparatus of the present invention. In the figure, (M) is a toothed mold in which teeth (H) and groove cavities (C) are alternately provided at a constant pitch on the outer peripheral surface. As shown in FIG. 2, flanges (F) (F) are provided on both sides to prevent the elastomer from flowing out. (E)
is an extruder with a nozzle (N) at its tip,
A heating lip (L) containing a heating device is attached to the nozzle (N) so that it can move up and down.
), the heating lip (L) is arranged so as to be substantially in contact with the surface of the toothed mold (M).

The extruder (E) heats and melts the input molding material, and the molten thermoplastic elastomer is injected into the cavity (C) of a toothed mold (M) equipped with a cooling mechanism inside.

Next, T approaches the front of the extruder (B) and molds with teeth (
A presser roll disposed so as to be able to roll with the rotation of M), and the presser roll (T) has a pressurizing function so that the thickness can be adjusted between the toothed mold (M) and the presser roll (T). ing.

Further, R is a guide roller of a molded timing belt, which rotates in contact with the rotation of the toothed mold (M) via the belt.

The manufacturing apparatus of the present invention has the above configuration. Next, a method for manufacturing a long timing belt using the manufacturing apparatus will be explained.

First, as shown in Fig. 3, flanges (F) (F
') (Fig. 2) The thermoplastic urethane elastomer (5) melted in the extruder (E) is injected onto the surface of the toothed mold (M) through the nozzle (N), and the mold (M) is
The mold (M) is then rotated in the direction of the arrow by the drive motor to move the injection cavity (C) in the rotational direction, and the cavity (C) is filled in order to form a compressed part. The elastomer (5) is continuously injected into C).

The urethane elastomer (5) injected into the cavity (C) from the nozzle (N) is melted and in a fluid state, but the urethane elastomer (5) is injected into the cavity (C) at the same time as it is injected into the cavity (C). In order to prevent the surface of the elastomer from hardening, the elastomer is heated and pressurized with a vertically movable heating lip attached to the nozzle (N) to lower the viscosity of the elastomer surface and soften it, making the surface smooth and suitable for heat fusion. do.

The molding materials used here are mainly thermoplastic urethane, but other polyester-based materials (DuPont brand name: Hytrel or Toyobo brand name: Helprene, etc.) and polyamide-based materials (Daicel brand name: Diamid-PAE)
Each thermoplastic resin may be used.

Next, by rotation of the mold (M), the softened belt compression part (4) having teeth is moved in the direction of the presser roll (T).

On the other hand, a tensile rope (1) formed by a known method
A hardened thermoplastic elastomer sheet (6) embedded in a predetermined position is inserted between the toothed mold (M) and the press roll with a constant tension via the press roll, and the softened belt compression portion ( 4), the belt molded body is formed by heat-sealing while pressing with a constant pressure to a predetermined thickness using a presser roll (T) whose thickness can be adjusted.

Here, the tensile lobes (1) are low elongation, high strength lobes made of steel cord, Kevlar (trade name: aromatic polyamide), polyester, glass fiber, etc., but are limited to lobes. It is not necessary to use various kinds of canvas or sudare.

Next, as the toothed mold rotates, the molded belt that has been heat-sealed and plasticized is cooled and hardened by the cooling mechanism of the mold (M), and the timing belt molded body (Tg) is placed on the guide roller (R).
) f! : Formed continuously.

The belt molded body (Tg
) is then wound up with a winder (not shown) or stored in some other suitable manner, and when used, it can be used as is or cut to a predetermined width to form a tensile material in the tensile part as shown in Figure 4. (1) is embedded, and the tooth part (3) with a constant pitch is located at the bottom.
A long thermoplastic urethane timing belt with ends can be obtained.

(Effects of the Invention) As described above, in the manufacturing method of the present invention, a flat thermoplastic sheet in which a tensile member is embedded is separately formed, and this sheet and an elastomer molded body forming a softened belt compression section are pressed together. By pressurizing and heat-sealing with rolls, it is possible to remove the internal residual shrinkage stress that could not be avoided with conventional manufacturing methods, and it is not only possible to continuously manufacture timing belts with uniform thickness and good quality. Depending on the requirements, it is also possible to continuously manufacture a belt with a two-layer structure in which the characteristics of the belt tooth portion and the tension portion are different.

Furthermore, the manufacturing method of the present invention does not require a conventional scale belt, which simplifies the equipment and simplifies maintenance management.

Furthermore, in the present invention, since the tensile body is not directly wound around the mold, there is no need to provide a nose on the mold, and the tensile body does not become polygonal and is positioned to match the pulley, so the dynamic quality of the belt is further improved. We can also expect it to improve.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the method for manufacturing a long timing belt according to the present invention, FIG. 2 is a partially enlarged sectional view taken along line A-A' of a rotary toothed mold used in the manufacturing method of the present invention, and FIG.
The figure is a partial enlarged view of the nozzle and presser roll used in the manufacturing method of the present invention, and FIG. 4 is a partial perspective view of a long timing belt obtained by the manufacturing method of the present invention. (1)...Tensile lobe (2)...Belt tension section (3)...Belt tooth section (4)...Belt compression section (5)...Thermoplastic elastomer (6)... ... Elastomer sheet (M) ... Rotating toothed mold (I () ... Toothed mold tooth section (C) ... Toothed belt groove cavity (E) ...
Extruder (N)...Nozzle (L)...Heating lip (T)...Press roll (R)...Belt guide roll (Tg)...Timing belt patent applicant Mitsuboshi Belting Co., Ltd. Figure 2 Figure 2

Claims (1)

[Claims] 1. A cavity is formed between a rotary toothed mold with flanges on both sides and a nozzle of an extruder, and molten thermoplastic elastomer is injected into the cavity through the nozzle, and is injected by rotating the mold. The elastomer is successively injected into the cavities by moving them in the rotational direction, and then a heating lip attached to the nozzle lowers the surface viscosity of the elastomer in the cavity to soften it, and extrudes the elastomer. Through a presser roll placed close to the front of the machine so that it can roll with the mold,
A hardened thermoplastic elastomer sheet with a tensile member embedded in a predetermined position is inserted between a toothed mold and a presser roll under constant tension, and the softened compressed portion is pressed with the presser roll until it reaches a predetermined thickness. A method for manufacturing a long timing belt, which comprises continuously forming a toothed belt molded body by heat-sealing and then cooling and hardening while rotating a toothed mold.