JPH0443768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing an elastic roller by an injection molding method.

[Prior Art] Conventionally, this type of elastic roller uses a synthetic rubber material as an elastic body that is attached to a core metal made of an iron rod or the like.

By the way, in the case of elastic rollers using conventional synthetic rubber materials as elastic bodies, synthetic rubber is kneaded with a reinforcing agent such as carbon, a softening agent such as oil, and a crosslinking agent such as sulfur, which is then shaped into a roller. It is molded and then heated and vulcanized.

Conventionally, synthetic rubber materials have been used to manufacture elastic rollers.

Therefore, many processes are required, and large-scale equipment is required for mass production.

In addition, the dimensional accuracy of the molded product is poor and large burrs may remain, requiring extensive secondary processing such as external polishing, resulting in high cost per roller and difficulty in mass production. .

Therefore, the present inventor developed a method of manufacturing elastic rollers by injection molding using thermoplastic elastomer instead of synthetic rubber. In some cases, the injection agent formed streak-like burrs, so-called parting lines.

Since the parting lines that occur with such injection molding are extremely small, the elastic rollers are simply used as paper feed rollers, transport rollers, etc. installed in electrophotographic copying machines. When using elasticity for applications that primarily generate frictional force, the parting line has no effect, but the roller itself is electrically conductive, or a separate thin conductive layer is applied to the outer circumferential surface of the roller. When the parting line is formed and charged directly by contacting the surface of the photosensitive drum, or when used in a transfer charger for transferring toner adhered to the photosensitive drum to transfer paper, the parting line should be aligned in the longitudinal direction. Due to the discontinuity, uniform charging properties cannot be obtained, which may lead to deterioration of image quality.

[Object of the Invention] The present invention was made in view of the above, and an object of the present invention is to provide a method for manufacturing an elastic roller by injection molding without forming parting lines on the surface of the roller. This is the purpose.

[Summary of the Invention] The gist of the present invention is to install a seamless pipe having an inner shape that matches the outer shape of the roller in a cavity formed in separate parts of an injection mold, The method of manufacturing an elastic roller is characterized in that the elastic roller is formed by injecting a thermoplastic resin material into the seamless pipe, and then the roller is pulled out from the pipe.

[Embodiments of the Invention] The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 shows a schematic cross-sectional view of an injection molding apparatus in which the present invention can be effectively implemented.

In the figure, 1 is a movable side mold for injection molding, 2 is a fixed side mold, and a metal seamless pipe 4 is removably installed in a cavity 7 formed in the opposing part of both molds 1 and 2. When opening the mold before the resin injection process, the seamless pipe 4 is installed and then the core bar 3 is inserted.
Alternatively, the elastic roller is attached to the seamless pipe 4 through the core bar 3 of the elastic roller. At this time, both ends of the core bar 3 are supported and fixed to both the molds 1 and 2 so as to be located at the axis of the seamless pipe 4. Further, a hot melt type adhesive is applied to the surface of the core metal 3 in advance to firmly adhere the elastic roller portion formed by injection molding to the core metal 3.

This seamless pipe 4 is made of the same material as the molds 1 and 2, for example, carbon steel, and its inner shape is formed to match the outer shape of the elastic roller.
For example, as shown in FIG. 4, when forming an elastic roller 8 with uniform outer dimensions in the axial direction,
The inner diameter is made uniform along the axial direction, and the inner surface is honed and then chrome plated to create an extremely smooth surface.

6 is a runner (resin material passage) provided in the stationary mold 2, and its spout is connected to the seamless pipe 4.
The thermoplastic elastomer resin material 5 is injected into the seamless pipe 4 .

Next, an elastic roller having the above configuration was manufactured in the following manner. The molds 1 and 2 kept at 70℃
After inserting the seamless pipe 4 and the mandrel 3 into the cavity 7 of the machine, the mold is closed, and the thermoplastic elastomer resin material 5 is styrene SEBS-based Lavalon T320C manufactured by Mitsubishi Yuka heated to 200°C. The mixture was injected at an injection pressure of 800 kg/cm ² (Figure 1). After cooling for 10 seconds, the molds 1 and 2 were opened, the molded product was taken out along with the pipe 4, and the runner portion 6 was cut with a cutter (Fig. 2).

Furthermore, when cooling from this state, a gap 6 will be created due to the difference in cooling shrinkage rate between the metal pipe 4 and the molded product roller 5.Use this to cool the roller for 2 minutes at room temperature, and then remove the roller. pipe 4
(Figure 3).

In this way, using a mold as shown in FIG. 1, the seamless pipe 4 is inserted into the mold, and then thermoplastic elastomer resin is molded by injection molding.
By releasing the mold, cooling it, and pulling out the roller from the pipe 4, it was possible to continuously manufacture elastic rollers with no burrs on the side surfaces, as shown in FIG. 4, at a rate of one roller every 30 seconds. Further, the secondary processing is very simple, just cutting the runner part, and as a result, the cost per roller is significantly lower than that of synthetic rubber.

As the thermoplastic elastomer resin, olefin elastomer, urethane elastomer, polyester elastomer, polyamide elastomer, vinyl chloride elastomer, fluorine elastomer, 1,2 polybutadiene elastomer, etc. can also be used.

Further, as for the elastic roller to be formed, in addition to the one shown in FIG. 4 whose diameter is constant in the axial direction, it may be one whose outer diameter differs in the axial direction as shown in FIGS. 5 a and b. In that case, the inner shape of the seamless pipe 4 only needs to match these outer shapes, and since the rollers have elasticity, by increasing the pulling force, the rollers can be pulled out from the pipe 4 while being elastically deformed. Can be done.

[Effects of the Invention] As explained above, a seamless pipe having an inner diameter corresponding to the outer diameter of the roller is inserted into the mold of an injection mold, and a thermoplastic elastomer resin material is injected by the injection molding method. After molding, for example, the roller is taken out of the mold together with the pipe, cooled, and then pulled out from the pipe. This makes it possible to manufacture an elastic roller with no burrs on the outer circumferential surface, making the processing process very simple. In addition to being easy to mass-produce, there is no need for roller external polishing, and only simple secondary processing such as gate cutting is required.

In addition, the molded resin can be cooled for a sufficient period of time after the pipe is removed from the mold, for example.
Inside the mold, only the minimum cooling time required to take out the roller along with the pipe is required, which greatly reduces the molding machine usage time per roller, and as a result, the production cost per roller can be reduced by using synthetic rubber. This can be significantly reduced compared to conventional elastic rollers.

Furthermore, by preparing seamless pipes with the same outer diameter and different inner diameters or shapes, it is possible to mold elastic rollers with different outer diameters or shapes using the same mold. You can get the same effect.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an embodiment of an injection molding apparatus that can effectively carry out the method of the present invention, and FIG.
The figure is a cross-sectional view of the pipe and roller molded product taken out from the mold after molding, Figure 3 is a cross-sectional view of the roller being pulled out from the pipe after cooling, Figure 4 is a side view of the elastic roller molded by the method of the present invention, and Figure 5 Figures a and b are side views showing other shapes of the elastic roller. 1... Movable side mold for injection molding, 2... Fixed side mold for injection molding, 3... Mandrel, 4... Seamless pipe, 5
...Thermoplastic elastomer resin material, 6. Runner, 7. Cavity.

Claims (1)

[Claims] 1. A seamless pipe having an inner shape that matches the outer shape of the roller is installed in the separately formed cavity of an injection mold, and a thermoplastic resin material is injected into this seamless pipe to form an elastic roller. A method of manufacturing an elastic roller, which comprises pulling the roller out of a pipe.