JPS5810172Y2 - tone arm - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of the tone arm of a record player.

As is well known, the tone arm has the role of supporting the pickup cartridge so that it always follows the record, in order to keep the end of the record stylus in close contact with the sound groove wall of the record and trace it correctly. It can be said that the playback response is determined mostly by the performance of the tonearm.

When considering the tone arm as a vibration system, the record stylus on the sound groove is connected to the tone arm by the compliance of its fulcrum, and the excitation force given by the sound groove is expressed as the vibration velocity.
It is reached via a shell to which a pickup cartridge is attached, a pipe arm, and a counterweight 1 for achieving gravitational balance.

On the other hand, although the tone arm is fixed to the turntable board by two support members that provide degrees of freedom corresponding to vertical and horizontal rotation, vibrations also spread to these mechanically connected parts.

These components that make up the tonearm, from the shell with the pickup cartridge attached to the pipe arm and the counterweight at its rear end, have some compliance and associated distributed mass, and if the vibration system If these factors are not taken into account, sharp resonances and anti-resonances will occur, which will not only disrupt the playback response in the bass range, but also increase or decrease the reaction force on the end of the record stylus, resulting in incomplete tracing and the above-mentioned vertical A slight wobbling of the support member that supports the tone arm rotatably in the horizontal direction causes undesirable adverse effects such as becoming a nonlinear element and contributing to waveform distortion.

FIG. 1 shows a simplified equivalent circuit diagram of a tone arm including a pickup cartridge focused on the bass range, and each element is considered in equivalent quantities.

That is, C8, r8 are the compliance of the fulcrum of the cantilever and its mechanical resistance, C&, Ca', Ca2...
represents the inherent compliance due to the joint points of the shell, pipe arm, etc. to which the pickup cartridge is attached, their members and shapes, m represents the mass interposed between them, and ml represents the counterweight. The mass and C1 are the coupling compliance of the portion of the counterweight that is coupled to the arm axis.

The bass output voltage response of the reproduction system is considered based on the speed V of the record stylus caused by the excitation force F at the end of the record stylus given by the sound groove of the record.

Although the compliance C3 of the fulcrum of the cantilever is sufficiently large, the associated mechanical resistance r8 is 20 in the high frequency range.
It only suppresses resonances above KH2, and is so small that it is of little use in the bass range considered here.

However, since the mass m1 of the counterweight, which is the largest in the tone arm vibration system, is relatively firmly connected to the main shaft of the pipe arm via the adjustment screw, its connection compliance C1 is generally extremely small.

Therefore, in the equivalent circuit of FIG. 1, the so-called non-matching state ends with the mass m1 of the counterweight, so the mass ma of the middle part of the tone arm and some compliances distributed therein cal ca' 9
Ca'... creates conditions that tend to cause resonance in the bass band.

In fact, in the conventional tone arm, as seen in the response curve example in FIG. 2, the mass m1 of the counterweight is
and l due to the compliance Cs of the fulcrum of the cantilever
The lowest fundamental resonant frequency f before and after OH2.

Some undulations appear in the main bass band around 30OH2, and at these resonance points the reaction to the end of the record stylus increases or decreases, making tracking unstable or howling likely to occur, or the turntable. It has undesirable negative effects such as being susceptible to mechanical vibration (rumple), which impedes high-fidelity playback.

The purpose of this invention is to provide a tone arm that eliminates the conventional drawbacks as described above, and FIG. 3 is a partially longitudinal side view showing an embodiment thereof, and the pipe arm 1 is A pivot 6, which is a second support member, is attached to a bracket 5 provided at the upper end of a shaft 4, which is a first support member, rotatably installed on the turntable board 2 via a bearing 3.
．． It is supported by 6 so as to be able to swing up and down.
The pipe arm 1 is supported so as to be horizontally rotatable and vertically swingable.

On the other hand, a shell 8 to which a pickup cartridge 7 is attached is fixed to the tip of the pipe arm 1.

Then, the record stylus 9 of the pickup cartridge 7 is placed in the sound groove 10a of the record 10 and is excited.Furthermore, a counterweight 11 is attached to the rear end of the pipe arm 1, and the desired stylus is set by gravity balance. A pressure W is applied to the record needle 9.

The feature of this invention is that the mounting of the counterweight 11 is improved as follows.

That is, this counterweight 11 has two parts, a front part 11a and a rear part 11b made of mild steel, connected by a joint threaded part 11c, and has a cavity 11d.

The threaded portion 1a at the rear end of the pipe arm 1 has a cylindrical thread 1.
2 are screwed together, and a cavity 11d of the counterweight 11 is fitted into this cylindrical screw 12, and one point of the counterweight 11 is connected to the cylindrical screw through a buffer ring 13 which is a buffer material provided at the entrance of the cavity 11d. 12, and between the vicinity of the center of gravity of the counterweight 11, which is another support point, and the cylindrical screw 12, it is supported via a diaphragm 14, which is another cushioning material.

That is, the outer periphery of the diaphragm 14 is inserted into the threaded portion 11c of the counterweight 11 together with the threaded portion, and
The inner periphery of the diaphragm 14 is fixed to the rear end of the cylindrical screw 12.

The counterweight 11 supported in this manner can be rotated by pinching its outer periphery with a fingertip, and can be slightly moved back and forth at the rear end of the pipe arm 1, thereby adjusting the needle pressure.

A braking disc 15 made of mild steel is concentrically fixed to the rear end of the cylindrical screw 12, and the outer periphery of the disc is fixed to the counterweight 11.
A narrow annular gap 16 is formed opposite to an annular projection 11e provided on the inner wall of the rear portion 11b.

A permanent magnet 17 having a partially spherical surface is fixed to the inner wall of the rear end of the twisted counterweight 11 so that the spherical surface faces the rear end of the brake disc 15, thereby forming a narrow dish-shaped gap 18. .

The annular gap 16 and the dish-shaped gap 18 are provided with the permanent magnet 1.
7 to supply magnetic flux and create a weak magnetic field of about 1 to 2 Gauss, respectively.

Then, an appropriate amount (approximately 2 to 3 c) of magnetic fine particles completely dispersed and suspended in viscous oil 19, that is, non-drying base oil, is injected into these voids.

As this non-drying base oil, fluorocarbon type or hydrocarbon type esters are suitable.

The above-mentioned viscous oil generally has a viscosity of about 2.000 cp (centipoise), and since the injected viscous oil has magnetic fine particles dispersed and suspended, it is attracted by the magnetic force of the above-mentioned magnetic field, and the above-mentioned annular shape on which the magnetic field always acts. Air gap 16 and dish-shaped air gap 18
It stays in the vicinity of the brake pad, and in addition to its own gravity or external impact, it does not leak out due to capillary action, and maintains a good braking effect almost permanently.

The action of this viscous oil 19 is represented by the braking resistance shown by r□ in the special circuit shown in FIG. Let's consider replacing it with the special price circuit.

Now, the fundamental resonance point f between the compliance C8 of the fulcrum of the record stylus and the total effective mass of the tone arm (m B + m 1 ).

If is set to around 10 H2 as usual, and the resonance point due to the effective mass (moment of inertia) of the turning movement about the center of gravity of the counterweight 11 (moment of inertia)) ml and the compliance C2 of the diaphragm 14 is set around 50 to 7 OH2, The vibration flowing into the tone arm from the end of the record needle gradually shifts from ml to C2 as the frequency increases,
Most of it passes through molecule 1.

Therefore, the reproduction system including the tone arm can be considered as a matched transmission system that terminates at rl, and even under suitable braking conditions, the compliance Ca, C/, C//... distributed in the middle of pipe arm 1, etc. Most of the harmful resonance caused by . etc. is removed, and a flat response as shown in FIG. 5 is obtained.

The diaphragm 14 is designed to support the counterweight 11 at its center of gravity and to provide flexibility for component forces in each direction.The diaphragm 14 is made of an oil-resistant soft film made of polyethylene or synthetic rubber with concentric circular corrugations. Appropriately,
This can prevent dust from entering and the viscous oil from leaking out.

The viscous oil 19 filling the annular gap 18 has a braking effect mainly on the vertical and horizontal turning movements of the tone arm shaft and the linear movement in the front and rear directions. This corresponds to the torsional vibration of the tone arm, and by both of these, almost all harmful vibrations exerted on the end of the record stylus can be removed and eliminated, resulting in a non-vibrating and quiet tone arm.

Moreover, since it has nothing to do with the movement of the support member that rotatably supports the tone arm in the vertical and horizontal directions, there is no need to worry about impeding the followability of the end of the record stylus.

In normal conditions, the counterweight 11 does not tilt because its center of gravity is supported, but when rotating the counterweight with your fingertips to balance the tone arm, the front portion 11a of the counterweight 11 In order to eliminate the possibility that the cylindrical screw 12 comes into contact with the cylindrical screw 12, the buffer ring 13 is interposed between these gaps.

In addition, in order to prevent the brake disc 15 provided at the rear end of the twist cylinder screw 12 from colliding with and adhering to the permanent magnet 17 due to an external impact, a small non-magnetic material is attached to the center of the rear end of the brake disc 15. A protrusion 20 is provided.

FIG. 6 shows a second embodiment of this invention,
The counterweight 11 is supported at two locations on the rear end of the pipe arm 1 fitted into the cavity 11d of the counterweight 11 via diaphragms 14 and 14' which are cushioning materials. Braking disc 15
Although the structure differs from that of the first embodiment in that a permanent magnet 17 is provided at the rear end, its function and effect are the same.

Further, in this embodiment, two diaphragms 14
．． 14', the counterweight 11 is divided into three parts with the attachment parts of the diaphragms 14 and 14' as a border, and each part is screwed together.
Although not shown in the drawings, the stylus pressure is adjusted by moving another weight back and forth.

As described above, this device attaches a counterweight to the rear end of the tone arm via a predetermined cushioning material so that it does not directly contact the rear end, and also connects the counterweight to the outer surface of the rear end. A tone arm is provided in which a gap is provided between the inner surface of the counterweight and the magnetic field is applied, and viscous oil in which magnetic fine particles are dispersed and suspended is retained in the gap as a braking resistor. It has the advantage of eliminating these drawbacks and providing high-fidelity reproduction without harmful resonance.

[Brief explanation of the drawing]

Fig. 1 is an equivalent circuit diagram of a general tone arm, Fig. 2 is a bass response characteristic diagram thereof, Fig. 3 is a diagram showing the first embodiment of the tone arm of this invention, and Fig. 4 is a diagram showing the third embodiment of the tone arm of this invention. The equivalent circuit diagram of the counterweight shown in the figure, Figure 5 shows an example of the low frequency response characteristics when using the tone arm of this invention, and Figure 6 shows the main part of the second embodiment of the tone arm of this invention. It is a diagram. 1... Pape arm, 2... Turntable board, 3... Bearing, 4... Shaft, 5... Bracket, 6
...Pivot, 7...Pickup cartridge,
8...shell, 9...record b'lr, 10-...
Record IL10a...Sound groove, 11...Counterweight, 11a...Front part of counterweight, 1
1b...rear part, 11c...joining screw part, 11d...
・Cavity, 11e... Annular projection, 12... Cylindrical screw, 1
3... Buffer ring, 14, 14'... Diaphragm, 15... Braking disk, 16, 18... Gap, 17
...Permanent magnet, 19...Viscous oil, 20...Small protrusion.

Claims (1)

[Scope of utility model registration request] A counterweight is attached to the rear end of the tone arm via a predetermined cushioning material so that it does not directly contact the rear end, and a magnetic field is created between the outer surface of the rear end and the inner surface of the counterweight. What is claimed is: 1. A tone arm characterized in that a gap is provided in which magnetic particles act, and viscous oil in which fine magnetic particles are dispersed and suspended is retained in the gap as a braking resistor.