JPS5913082B2 - Pickup cartridge cantilever - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a special structure of a cantilever of a record player's backup cartridge.

The cantilever for the big-up cartridge is designed to have high rigidity so that split vibrations do not occur, and the equivalent mass seen from the tip of the needle to be as small as possible, so that the reproduction band of the cartridge can be extended to the high frequency range. In addition, it is desired that the manufacturing process be easy and that the properties be uniform. By the way, as a conventional cantilever, as shown in FIG. 1, an aluminum alloy is integrally formed into a hollow shape by drawing.

That is, in the figure, 1 is a cantilever, 2 is a stylus, and 3 is a magnet. However, aluminum has a small longitudinal elastic modulus of 9/1 of 7000, and a relatively high density of 2.7θ/d0. Therefore, in a cartridge using a conventional aluminum cantilever, the reproduction frequency characteristics A so-called sag phenomenon occurs in which the output decreases in the high range, resulting in a deterioration in sound quality, and the playback limit frequency also has the drawback of not being able to rise very high.

In order to increase the reproduction limit frequency, it is sufficient to reduce the equivalent mass, and for this reason, the cantilever 1 made of aluminum
As described above, the cantilever is made hollow and the inner thickness is made as thin as possible, but this causes the disadvantage that the rigidity of the cantilever decreases and the above-mentioned deflection phenomenon becomes more pronounced. On the other hand, the applicant has previously proposed that the epoxy resin has a diameter of 7μ and a length of several meters77.
! There is a method in which a composite material is formed by mixing a large number of thin carbon fiber wires selected from the above at a desired mixing ratio, and the composite material is heated and molded into a desired shape.

The present invention applies the technology proposed by the applicant as described above to increase the rigidity and reduce the equivalent mass, thereby improving the reproduction frequency characteristics of the cartridge and improving high-frequency resonance. The present invention provides a sword angler with a novel structure having a vertical angle that improves crosstalk near frequencies.

An embodiment in which the present invention is applied to a moving magnet type cartridge will be described in detail with reference to FIGS.

In FIG. 2, reference numeral 4 indicates a cantilever. A stylus 5 is fixed to one end of the cantilever 4, and a magnet 6 is attached to the other end.

A pole piece 7 is wound with a coil 8, and a cantilever 14 is supported by the pole piece 7 via a damper 9.

As shown in FIGS. 2 and 3, the cantilever 4 has one end on which the stylus 5 is attached as a flat plate part (stylus attachment part) 4a, and the other end as a tapered cylindrical part extending from the stylus attachment side to the magnet attachment side. This is section 4b.

That is, on the other end side, a hollow part 4c is formed which has a depth of about 2/3 of the length of the cylindrical part 4b from the magnet mounting side. This hollow portion 4c has a straight shape on the magnet attachment side and a tapered shape on the opposite side. and,
At the intersection of the flat plate part 4a and the cylindrical part 4b, the direction of the flat plate part 4a is inclined at an angle θ with respect to the direction of the cylindrical part 4b. This inclination angle θ is called a so-called vertical angle, and its effect will become clear from what will be described later.
A through hole 1 for fixing a stylus is provided in the center of the flat plate portion 4a.
1 is formed. Next, the manufacturing process of the cantilever according to the present invention will be described.

First, the material used for the cantilever 14 is a so-called prepreg sheet.

This prepreg sheet is a composite material of carbon fiber and thermosetting resin such as epoxy resin. For example, carbon fibers commercially available under the trade name "Torayka" have a fiber diameter of 5 to 7μ, a modulus of longitudinal elasticity of 20000 kg/Md or more, a tensile strength of 200 k9/Md or more, and a density of 1.789/Md.
C77t is extremely suitable due to its high strength, high elasticity, and low density. In this example, a carbon fiber having a volume content of 50 to 55% with respect to the thermosetting resin is used. The so-called prepreg sheet 12 thus formed is cut into strip-shaped sheets with directionality, as shown in FIG. 4 (arrows in the figure indicate fiber directions).

That is, a strip-shaped sheet 1 having fibers in the longitudinal direction.
2a1 For example, three types of sheets, ie, a rectangular sheet 12b tilted toward the left 45 and a rectangular sheet 12c tilted toward the right 454, are sequentially stacked to have a thickness of about 0.2 to 0.25 mm. Molding a cantilever using a rectangular sheet
This is because we considered the ease of molding, especially the ease of molding the stylus attachment part with a vertical angle, and therefore the improvement of yield. Also, three types of strip-shaped sheets 12a to 12c with different fiber directions are used. The reason for using this is to make the characteristics of the cantilever 14 after molding uniform in the vibration direction of the cantilever 14.

The laminated and polymerized strip-shaped sheet (polymer) is heat-formed into a cantilever shape using a heat press mold apparatus as shown in FIG.

This heat press mold device will be explained with reference to FIG. An upper die 14 and a lower die 15 of a heat press mold are arranged, and heaters 16a and 16b for heating the strip-shaped sheet are arranged in the upper die 14 and the lower die 15, respectively, and the strip-shaped sheet is formed into two layers, upper and lower. A core 20 is sandwiched between the sheets 13. This core 20 has a shape that can form a hollow portion 4c formed in the cantilever 14 described above. Lower mold 1
As shown in FIG. 6, the cantilever 5 has a female mold 17 having a lower half cross section of the cantilever 14, and a guide pin 18 for inserting the mold is planted on the surface in contact with the upper mold 14. Type 17
consists of a portion 17a for the flat plate portion 4a of the cantilever 14 and a portion 17b for the cylindrical portion 4b, and this portion 17
A vertical angle θ is set at the intersection of a and 17b.

Therefore, the upper mold 15 also has a structure imitating this lower mold.
That is, the upper die 15 has a female die constituting the upper half cross section of the cantilever 14 and a through hole into which the guide pin 18 of the lower die 14 is inserted. Next, to explain the manufacturing process of the cantilever, a so-called two-layer prepreg sheet is sandwiched together with the core 20 in the heat press mold configured as described above.

The volume content of the prepreg sheet is as described above, but in order to increase the volume content after molding, prevent board formation, and improve strength, the volume content is greater than the cross-sectional area of the upper and lower molds 14 and 15. is desirable. The prepreg sheet set in a predetermined position is fixed by the upper and lower molds 14 and 15, and the upper and lower molds 14 and 15 are pressed by the heaters 16a and 16b to form the pair of upper and lower strip-shaped sheets 13 into a third Join them so that they form the shape shown in the figure. In this example, a pressure of 10 kg was applied to the prepreg sheet having the above volume content.
/Cril is added, and the mixture is further maintained for about 30 minutes in an atmosphere at a temperature of around 17°C. After heat-forming, the so-called burrs of the epoxy resin are cut and shaped to complete a cantilever having a vertical angle. In this case, in order to make the material of the hot-formed cantilever appropriate, it is better to anneal the molded cantilever for about 2 hours before cutting and shaping the cantilever. A through hole 11 for attaching the stylus 5 is then made in the center of the flat plate portion 4a of the cantilever, and the stylus 5 is fixed as shown in FIG. In this case, the through hole for attaching the stylus drilled in the flat plate part can be formed by forming a core in either of the upper or lower molds 14 and 15 described above, and the core can be used during heat molding. The through hole 11 is integrally formed, which can reduce the number of man-hours in the manufacturing process, and the stylus mounting portion 19 is made concave as shown in FIG. 8 without forming a through hole in the flat plate portion of the cantilever. The stylus 5 can be fixed to this portion 19 with adhesive. Therefore, according to the cantilever 1 having a hollow portion according to the present invention, even when its cross-sectional area is made to be about the same as that of a conventional cantilever made of an aluminum pipe, it has a smaller cross-sectional area than that of a conventional cantilever made of an aluminum pipe. The stiffness increases significantly,
And the equivalent mass becomes smaller.

Therefore, according to the pick-up cartridge using the cantilever of the present invention, the reproduction frequency characteristics can be improved. That is, in the case of a conventional cartridge using a cantilever made of an aluminum pipe, a so-called sagging phenomenon occurs in which the output decreases from the mid to high range, and the reproduction limit frequency does not become very high. A cartridge using a cantilever has high rigidity, so no sagging phenomenon occurs and the sound quality is improved, and since the equivalent mass is small, the reproduction limit frequency becomes significantly high.

Furthermore, the separation characteristics are greatly improved compared to those using conventional cantilevers made of aluminum pipes. Furthermore, since a so-called vertical angle is set at the cantilever, crosstalk near the high-pitched resonance frequency is significantly improved. Note that the synthetic resin does not need to be an epoxy resin, and may also be a phenolic resin or a polyester resin. The shape of carbon fiber is also just one example.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view showing the structure of an example of a conventional cantilever, FIG. 2 is an enlarged sectional view showing the structure of an example of a cartridge using the cantilever according to the present invention, and FIG. 3 is an enlarged sectional view showing the structure of an example of the cantilever according to the present invention. An enlarged perspective view showing the structure of an example of
FIG. 4 is a schematic plan view for explaining the prepreg sheet, FIG. 5 is a structural diagram showing an example of implementing the present invention,
FIG. 6 is a partially omitted enlarged perspective view showing an example of the lower die, and FIGS. 7 and 8 are explanatory views of main parts for explaining the cantilever. 4 is a cantilever, 5 is a stylus, 12 is a prepreg sheet, 13 is a strip-shaped prepreg sheet, 14 is an upper mold, 15 is a lower mold, 16a and 16b are heating heaters, 17 is a female cantilever of the lower mold. The mold, 20, is the core.

Claims (1)

[Claims] 1 A plastic sheet polymer made by stacking a plurality of plastic sheets containing carbon fiber as a main component so that the fiber directions are different from each other is arranged on either side of an upper mold and a lower mold having a vertical angle, A cantilever for a pickup cartridge, characterized in that the above-mentioned plastic sheet polymer is compressed and heated so that a vertical angle is attached to the tip thereof, and the other end is formed to form a hollow lever portion.