Tone arm assembly

A tone arm assembly in which an upper plate is given added strength by providing it with apertures only in the region of the drive motor and the tone arm support shaft without the need of a long aperture to accommodate the entire tone arm assembly. The tone arm shaft is rotatably supported through a first rotatable member onto a second rotatable member and finally to a vertical support shaft. A connecting member and weight shaft are detachably coupled to the first rotatable member through damper means. Prior to attachment of the connecting member and weight shaft, the tone arm shaft can be rotated in a vertical plane through an angle of approximately 100.degree..

BACKGROUND OF THE INVENTION 
The present invention relates to a tone arm assembly for record players. 
A typical tone arm assembly of the prior art will be described with 
reference to FIGS. 1 and 2. In this tone arm assembly, a base plate 3 is 
supported by support posts 1 through spring members 2. A tone arm support 
base 6 and drive motor 5 for driving a turntable 4 are secured to the base 
plate 3 and are covered with an upper panel 7 supported on the upper 
portions of the support posts 1. The turntable 4 is turned on a spindle 5a 
of the motor 5. In order to facilitate the manufacture of this assembly, 
necessary parts are installed on the base plate 3 before the upper panel 7 
is set in place surrounding the remaining parts. 
Although the horizontal rotational movement of the prior art tone arm 8 is 
relatively free, the vertical rotational movement thereof is restricted to 
only a small range of up-and-down movement. Because of this restriction, 
for installation of the upper panel 7 during the final steps of assembly, 
it is necessary to form therein a relatively long and large hole 7a 
through which the tone arm 8 extends. The hole 7a joins with a hole 7c for 
the spindle 5a of the motor 5 and with a hole 7b for the tone arm support 
base 6. With such a construction, the upper panel is weak in mechanical 
strength. In order to compensate for the insufficient mechanical strength 
thereof, a second reinforcement panel is required resulting in a high 
cost. 
SUMMARY OF THE INVENTION 
In view of the above noted defects, an object of the present invention is 
to provide a tone arm assembly in which a tubular arm shaft of a tone arm 
can be raised to a sufficient extent by separation of a weight shaft 
therefrom and in which the interchange of the weight shafts can be readily 
achieved. 
This, as well as other objects of the invention, are met by a tone arm 
assembly including a first rotatable member joined to one end of a tone 
arm shaft at the other end of which is located a phonocartridge. The first 
rotatable member is rotatably connected to a second rotatable member. A 
connecting member to which is coupled a weight shaft is detachably mounted 
on the first rotatable member. Prior to the attachment of the connecting 
member and weight shaft to the first rotatable member, the tone arm shaft 
can be rotated through an angle of approximately 100.degree., as defined 
by stop means provided on the first rotatable member, so that an upper 
plate can easily be installed. The connecting member may be joined to the 
first rotatable member through damper means and the weight shaft can also 
be joined to the connecting member through a second damper means. With 
this construction, the upper plate need only have apertures corresponding 
to the turntable or motor shaft and the vertical shaft to which the second 
rotatable member is coupled and no large long aperture is required to 
accommodate the entire length of the tone arm assembly thereby giving the 
upper plate increased strength when compared to the structure of the prior 
art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The invention will hereinafter be described with reference to FIGS. 3, 
4A-4C, and 5A and 5B of the accompanying drawings. FIG. 3 is an exploded 
view showing a tone arm 11 provided at an end with a pick-up 
phonocartridge 10 including a head cover 9. The tone arm 11 is coupled at 
the other end to a first rotatable member 12. The first rotatable member 
12 is rotatably mounted on a second rotatable member 13 with pivot screws 
14 engaged with side walls of the second member 13. A connecting member 17 
to which is coupled a weight shaft 16 is mounted on the first rotatable 
member 12 by a pair of screws 15 which are screwed in downwardly with the 
longitudinal axis of the arm shaft 11 being aligned with that of the 
weight shaft 16 by the connecting member 17. 
FIGS. 4A to C show details of the first and second rotatable members 12 and 
13. A pair of stops 12a are formed at the upper rear edge of the first 
rotatable member 12 on opposite sides of the arm shaft 11. As shown in 
FIG. 4C, upon vertical rotation of the tone arm, the stops 12a are brought 
into abutment with a bottom portion 13a of the second rotatable member 13 
to thereby limit the vertical rotational angle of the tone arm to 
approximately 100.degree.. Reference character 12b designtes a pair of 
threaded holes for receiving the screws 15 and 12c designates a groove 
with which the peripheral wall of the connecting member 17 engages. 
A tubular vertical shaft 18 is fixedly secured to the bottom portion 13a of 
the second rotatable member 13. Signal lines (not shown) connected to the 
pick-up cartridge 10 through the interior of the arm shaft 11 are arranged 
in an interior of the vertical shaft 18 through a U-shaped portion 12d of 
the first rotatable member 12. The vertical shaft 18 is received by a 
bearing 19 installed on the tone arm support base 6 as shown in FIG. 4C. 
FIGS. 5A and 5B show the relationship between the weight shaft 16 and the 
connecting member 17. The weight shaft 16 is connected to the connecting 
member 17 through a damper rubber member 20 by a screw 21. A lower portion 
of the weight shaft 16 is cut to form a strip-shaped portion 16a which is 
provided with a projection 16a.sub.1. A weight 22 is pressingly engaged 
with the weight shaft 16 at the projection l6a.sub.1 and is movable fore 
and aft by rotation of the weight 22. Rubber packings 23 are provided on 
the rear side of the connecting member 17 at a pair of mounting holes 17a 
to thereby impart a damper effect to the mounting portion of the first 
rotatable member 12. With this construction, resonance of the tone arm is 
effectively damped or prevented. 
On both sides of the connecting member 17 are formed apertures 17b from 
which the screws 14 of the second rotatable member 13 project. Upright 
walls 17c are formed inside the apertures 17b which define the rotational 
range of the second rotatable member 13 when the connecting member 17 is 
mounted on the first rotatable member 12 by the screws 15. That is, with 
respect to the connecting member 17, the distance l.sub.1 between the 
confronting upright walls 17c is set somewhat greater than the width 
l.sub.2 of the side walls 13b of the second rotatable member 13 so that 
the connecting member 17 once mounted on the first rotatable member 12 is 
vertically rotatable upon the second rotatable member 13 to a limit 
corresponding to the dimensional difference therebetween. With this 
construction, when fully assembled, the tone arm is movable up and down by 
a limited amount as desired. 
As described above, according to the present invention, the same desired 
operation as in the prior art construction is obtained when the tone arm 
is fully assembled. That is, a large angle of rotation of the arm shaft 11 
is permitted in the horizontal direction and a much smaller angle of 
rotation thereof is permitted in the vertical direction. Also, if the 
screws 15 are removed so as to separate the connecting member 17 and 
weight shaft 16 from the first rotatable member 12, the arm shaft 11 can 
be rotatably raised to an angle of approximately 100.degree. and retained 
in this condition. 
Thus, in the assembly of the record player according to the present 
invention, the arm shaft 11 can be raised to a vertical position. 
Therefore, only the hole 7b for the tone arm support base 6 and the hole 
7c for the turntable spindle 5a need be provided in the upper panel 7 as 
shown in FIG. 6. That is, the long longitudinal slot 7a (shown in FIGS. 1 
and 2) for the insertion of the tone arm can be dispensed with. In the 
prior art construction, the hole 7a must extend under the turntable. 
Therefore, according to the present invention, the problem of lack of 
mechanical strength of the upper panel 7 is eliminated. Also, when the 
tone arm is fully raised, it is possible to readily exchange the cartridge 
in the case where the head cover cannot be removed. According to another 
aspect of the present invention, since the connecting member and the 
weight shaft are separable from the arm shaft, the materials used therefor 
and the stiffness of the vibration damper materials therefor can be varied 
widely so that the natural resonance frequency of the tone arm can be 
varied. Reproduction frequency characteristics can be readily changed. At 
the same time, any desirable design or color can be freely used to thereby 
change the appearance of the tone arm assembly.