JPS6114563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an arm pipe for playing records.

In recent years, in order to improve the tracing ability of cartridges, there has been a trend to reduce the mass of the vibration system and increase compliance.

However, when the compliance of the cartridge is increased, the low-frequency resonance frequency generated by the compliance of the cartridge and the equivalent mass of the tip of the tone arm including the cartridge becomes lower, and noises caused by eccentricity and warping of the record are picked up. /N gets worse. Therefore, the equivalent mass of the needle tip must be small and the low-frequency resonance must be set to an appropriate value (10 to 15 Hz is generally considered good).

By the way, in order to reduce the equivalent mass of the needle tip, it is possible to make the arm pipe and head shell lighter, but if the wall thickness is made thinner in order to make them lighter, the rigidity will decrease, making unnecessary split resonance more likely to occur, which will reduce the sound quality. Often causes deterioration. Therefore, in order to manufacture arm pipes and head shells that are both highly rigid and lightweight, materials with a high specific modulus of elasticity are required.

However, conventionally used materials such as aluminum and titanium have relatively high specific modulus, but in order to manufacture arm pipes and head shells that are used in combination with cartridges with high compliance, it is necessary to have even higher specific modulus. Requires large materials.

In addition, there are arm pipes and head shells made of carbon fiber, but this carbon fiber has a high specific modulus of elasticity, but in order to be molded into arm pipes and head shells, it is necessary to combine it with resin. However, when composited with resin, the overall specific elastic modulus becomes small, equal to or lower than the above-mentioned aluminum and titanium, making it unsuitable as a material for arm pipes and head shells.

This invention was made in view of the above points,
Of the arm pipe and head shell, the arm pipe is made of a material with a high specific elastic modulus obtained by kneading resin and graphite powder and orienting the graphite powder, creating a lightweight, highly rigid, and high-performance arm pipe. An object of the present invention is to provide a method for manufacturing an arm pipe that can be manufactured.

Another object of the present invention is to provide a method for manufacturing an arm pipe by rolling a material obtained by kneading resin and graphite powder into a flat plate, orienting the graphite powder, and then forming the material into a pipe shape.

Next, to explain the materials used in this invention, for example, vinyl chloride (hereinafter referred to as PVC) is used as the resin, and 30 parts of PVC and 70 parts of graphite powder are heated at 130°C.
After mixing well on a roll at a temperature of ~200℃,
The flat plate obtained by rolling has a Young's modulus of 6000Kg/
mm ² , and the density is 1.8 g/cm ³ . Therefore, the specific elastic modulus is
The specific elastic modulus of aluminum and titanium is 3.3×10 ⁹ mm, which is approximately 1.3 times larger than that of aluminum and titanium, which have a specific elastic modulus of 2.6×10 ⁹ mm.

Furthermore, this material was heated to 250℃ in an oxidizing atmosphere.
After pre-calcining by heating while gradually increasing the temperature at a rate of ~10℃/H, carbonizing by heating at a rate of 10 to 20℃ in a non-oxidizing atmosphere or in vacuum to 1200℃ increases the Young's modulus. is 25000Kg/mm ² and the density is 1.7g/cm ³ . Therefore, the specific elastic modulus is 1.5×10 ¹⁰ mm, which is about 5.5 times that of aluminum and titanium.

However, the above-mentioned materials require graphite powder to be oriented, and simply kneading PVC and graphite powder and molding by extrusion or the like will not increase the Young's modulus. For example, 30 parts of PVC mentioned above and graphite powder
The Young's modulus of a material that is mixed and kneaded at a ratio of 70 parts and extruded into a flat plate using an extrusion molding machine is approximately 1300 Kg/ ^mm2 , which is 1/4.5 of that of oriented graphite powder. decreases to Furthermore, the carbonized material has a Young's modulus of 4000 Kg/mm ² , which is only about 1/6 of that obtained by oriented graphite powder.

As explained above, the material made by kneading resin and graphite powder (hereinafter referred to as the present material) has a higher specific elastic modulus than other materials, and is excellent as a material for making lightweight and highly rigid arm pipes. Furthermore, the internal loss of this material is tanδ=0.05, which is equal to that of aluminum.
tanδ=0.003, compared to titanium tanδ=0.005, approx.
It is 10 times larger and therefore less likely to cause unnecessary resonance, making it an ideal material for arm pipes.

In order to construct an arm pipe by taking advantage of the characteristics of this material, it is necessary to orient the graphite powder inside the arm pipe. The powder is not oriented and the Young's modulus is not high.

A method for manufacturing an arm pipe according to the present invention will be described below.

Figure 1a shows a material made by kneading resin and graphite powder (hereinafter referred to as the kneaded material), in the figure 1 is the resin part, 2 is the graphite powder in the resin, which has a scale shape.
From a macroscopic perspective, it can be seen as a disk with a large diameter relative to its thickness. When the resin and graphite powder are simply kneaded, the orientation of the graphite powder 2 is random as shown in the figure. Therefore, when the above-mentioned kneaded material is rolled into a flat plate using a roller or a press, a flat plate 3 is formed as shown in Fig. 1b.
Only the graphite powder inside is oriented parallel to the surface of the flat plate 3.

The thickness of the flat plate 3 is determined in accordance with the thickness of a predetermined arm pipe. The flat plate 3 is rounded to fit the diameter of the arm pipe as shown in FIG. 1c, and the seam 4 is formed by heating and pressure bonding when rounding the flat plate 3, or by bonding with a suitable adhesive.

As shown in FIGS. 1c and d, the arm pipe 5 manufactured by the above manufacturing method has graphite powder 2 in the arm pipe oriented parallel to the surface of the arm pipe 5, resulting in a highly rigid arm. You can get a pipe. Note that the length may be made to match the length of a predetermined arm pipe, or a long pipe may be manufactured and cut to a predetermined length.

The graphite powder used = 2 preferably has an average particle size of 20 μm or less, particularly 5 μm or less. Further, as the resin part 1 to be mixed with the graphite powder 2, vinyl chloride, vinylidene chloride, a copolymer of vinyl chloride and acrylonitrile, a copolymer of vinylidene chloride and acrylonitrile, a copolymer of vinyl chloride and vinyl acetate, etc. A single substance or a combination of these resins are suitable.

After being formed into the arm pipe 5 described above, it is heated to 250°C in an oxidizing atmosphere while gradually increasing the temperature at a rate of 1°C to 10°C/H to pre-fire it to make it infusible, and then to make it non-oxidizing. 1200℃ in atmosphere or vacuum
When heated at a temperature increase rate of 10℃ to 20℃ until carbonization,
The rigidity of the arm pipe 5 is improved by about four times compared to before carbonization.

Note that the arm pipe 5 may be deformed during the pre-firing described above, so either insert a mold to prevent deformation (made of a material that does not deform even at temperatures of 250°C or higher) into the inner diameter of the arm pipe 5, or mold the outer periphery of the arm pipe 5. It needs to be pressed with a mold. Furthermore, after pre-firing, there is no need to press it with a mold because no deformation occurs even if it is heated to 1200°C and carbonized.

When the carbonization temperature is further increased to graphitize at 2500°C or higher, the rigidity of the arm pipe 5 becomes approximately 1.5 times greater than that when carbonized at 1200°C.

In addition, 6 in FIG. 2 is a head shell, 7 is a balance weight, and 8 is an arm shaft.

As described above, this invention makes it possible to obtain a lightweight and highly rigid arm pipe by orienting the graphite powder. Therefore, it is possible to manufacture an arm pipe with a small needle tip equivalent mass, and even when combined with a cartridge with a large compliance, it is possible to obtain a lightweight and highly rigid arm pipe. It becomes difficult to pick up noise caused by warpage or eccentricity, allowing playback with a good S/N ratio. In addition, since the internal loss is large, unnecessary resonance and split vibration are unlikely to occur, and high-quality sound reproduction is possible.Furthermore, it is easy to mold, and the material cost is low, resulting in lower product costs.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing the manufacturing process of the arm pipe manufacturing method according to the present invention, and FIG. 2 is a side view showing the entire tone arm including the arm pipe manufactured by this manufacturing method. 1...Resin part, 2...Graphite powder, 5...Arm pipe.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an arm pipe, which comprises rolling a material obtained by kneading resin and graphite powder into a flat plate, orienting the graphite powder, and then forming the material into a cylindrical shape. 2. A method for manufacturing an arm pipe, which comprises rolling a material obtained by kneading resin and graphite powder into a flat plate, orienting the graphite powder, forming the material into a cylindrical shape, and carbonizing or graphitizing the material.