JPS5913081B2 - 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 of the pickup cartridge is required to have high rigidity and no splitting vibrations in order to extend the reproduction band of the cartridge to the high frequency range, and to have the equivalent mass as seen from the tip of the needle as small as possible and the specific gravity of the material to be low. Furthermore, it is desired that the manufacturing is easy and the properties are 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. In other words, in the same figure, 1 is the cantilever, 2 is the stylus,
3 is a magnet. However, the longitudinal elastic modulus E of aluminum is as small as 9/1 to 7000, and the density is 2
．． It is relatively large at 7g/10cm, and as a result, in cartridges using conventional aluminum cantilevers, due to the reproduction frequency characteristics, a so-called sag phenomenon occurs in which the output decreases from the midrange to the treble range, resulting in a decline in sound quality. Also, there was a drawback that the reproduction limit frequency was not as high as 15.

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 results in the disadvantage that the steel 20 properties of the cantilever are reduced and the above-mentioned deflection phenomenon becomes more pronounced. Therefore, the present applicant had previously proposed an epoxy resin with a diameter of 7μ and a length of several mm.
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 of 25, and the composite material is heated and molded into a desired shape.

The present invention applies the technology proposed in the present application as described above, and as the steel strength increases, the equivalent quality decreases, and therefore the reproduction frequency characteristics of the cartridge can be improved, and high-pitched The present invention provides a cantilever with a novel structure having a vertical angle that improves crosstalk near the resonance frequency.

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 has a coil 8 wound around it, and a cantilever 14 is supported by the pole piece 7 via a damper 9.

As shown in FIGS. 2 and 3, the cantilever 14 has one end to which the stylus 5 is attached as a flat plate portion 4a, and the other end as a straight cylindrical portion 4b.

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. Further, a through hole 11 for fixing a sliver is formed in the center of the flat plate portion 4a. 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.

The purpreg sheet is a composite material of carbon fiber and thermosetting or thermoplastic resin such as epoxy resin. For example, the carbon fiber commercially available under the trade name "Trading Card" has a fiber diameter of 5 to 7μ and a longitudinal elastic modulus E of 20,000k.
9/I! d or more, tensile strength is 200k9/Md or more,
Density is 1.789/c! Due to its high strength, high elasticity, and low density, it is an extremely suitable material for forming the cantilever. In this example, the volume content of carbon fiber to thermosetting resin is 50 to 55 (f) in the prepreg sheet state.
Use the one. The so-called prepreg sheet 12 thus formed is used by being cut into strip-shaped sheets having directionality, as shown in FIG. 4 (the missing marks in the figure indicate the fiber directions).

That is, three types of sheets: a strip-shaped sheet 12a having fibers in the longitudinal direction, a strip-shaped sheet 12b tilted toward the left 45 fibers, and a strip-shaped sheet 12c tilted toward the right 454 fibers are sequentially stacked to form a fiber of 0.2 to 0. Make it about 25mm thick. The reason why the cantilever is molded using a strip-shaped sheet is to facilitate molding, especially the ease of molding the stylus attachment part with a vertical angle, and to improve yield. The reason why three different types of strip-shaped sheets 12a to 12c are used is to make the characteristics of the cantilever 14 after molding uniform with respect to the vibration direction of the cantilever 14.

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

This heat press mold device will be explained with reference to FIG. An upper mold 14 and a lower mold 15 of a heat press mold are arranged, and heaters 16a and 16b for heating a strip-shaped sheet are arranged in the upper mold 14 and the lower mold 15, respectively. As shown in FIG. 6, the lower mold 15 has a cantilever female mold 17 having a lower half 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. and the female die 17 is attached to a portion 17a of the cantilever 14 relative to the flat plate portion 4a.
and a portion 17b relative to the cylindrical portion 4b, and a vertical angle θ is set at the intersection of these portions 17a 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 between 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 at a predetermined position is fixed by upper and lower molds 14 and 15, and heaters 16a and 16b press the upper and lower molds 14 and 15 to form a pair of upper and lower strip-shaped sheets 13 as shown in FIG. Join them so that they form the shape shown in . In this example 1, a pressure of 10 k was applied to the prepreg sheet having the above volume content.
1! /Cril is added, and the mixture is further maintained for about 30 minutes in an atmosphere at a temperature of around 170°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 select the appropriate material for the thermoformed cantilever,
It is better to perform annealing for about 2 hours before cutting and shaping the cantilever after molding. 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, by providing a core in either of the upper and lower molds 14 and 15 described above, the through hole for attaching the stylus drilled in the flat plate part can be formed through the through hole during heat forming. Since the hole 11 is integrally formed, the man-hours in the manufacturing process can be reduced, 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 the portion 19 with adhesive. Therefore, according to the cantilever according to the present invention, even if its cross-sectional area is made to be about the same as that of a conventional cantilever made of an aluminum pipe, its rigidity is significantly greater than that of a conventional cantilever made of an aluminum pipe. and the equivalent mass becomes considerably smaller.

Therefore, according to the pick-up cartridge using the cantilever of the present invention, the reproduction frequency characteristics can be improved.

In other words, 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 midrange to the high frequency range, and the reproduction limit frequency does not become very high. According to the cartridge used, the rigidity is large, so no sagging phenomenon occurs, and the sound quality is improved, and the reproduction limit frequency is also significantly increased because the special mass is small. 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 level, crosstalk near the high-pitched resonance frequency is significantly improved. 9 and 10 show another example of the present invention. In this example, the shape of the cantilever 14 is changed to a cylindrical portion as shown in FIG. 9, taking into consideration the equivalent mass of the vibration system. 4b is tapered from the stylus mounting side to the magnet mounting side.

Therefore, the heat press mold is also designed to be able to form this tapered cantilever, and as shown in FIG. 10, a cantilever female mold 21 is formed in the lower mold 20 thereof. Therefore, it goes without saying that the above-mentioned effects can be obtained in this example as well, and further, because of the tapered shape, the equivalent mass of the vibration system can be reduced.

Note that the resin does not need to be an epoxy resin, but can also be a phenolic resin or a polyester resin, and the shape of the carbon fiber is also just an example.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of an example of a conventional cantilever, FIG. 2 is a cross-sectional view showing the structure of an example of a cartridge using the cantilever according to the present invention, and FIG. 3 is an example of the cantilever according to the present invention. FIG. 4 is an enlarged perspective view showing the structure of the prepreg sheet, FIG. 5 is a schematic enlarged plan view for explaining the prepreg sheet, FIG.
The figure is a partially omitted enlarged perspective view showing an example of the lower die, FIGS. 7 and 8 are explanatory views of main parts for explaining the cantilever, and FIGS. 9 and 10 are other examples of the present invention, respectively. FIG. 4 is a cantilever, 5 is a stylus, 12 is a prepreg sheet, 13 is a strip prepreg sheet, 14 is an upper mold,
15 and 20 are lower molds, 16a and 16b are heaters, and 17 and 21 are female cantilever molds of the lower mold.

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 a stylus attachment portion having a vertical angle is formed at a free end portion by compressing and heating the above-mentioned plastic sheet polymer.