US2681228A - Tone arm - Google Patents

Description

June 15, 1954 l.. J. ANDRES 2,681,228

TONE ARM Filed Feb. 26, 1952 Patented June 15, 1954 UNITED STATES `'07F F ICE Lloyd-Andrea Chicag o, 111.,.assigncr to Bernie,

Incorporated, JChicago,i1ll.,` ,acorporation l Application February `26, 1952, Serial Nc.`273,'381

1 Claim. l

This invention relates in `.general to phono- .graphs `andinore particularlytoa tone arm for .playing disc records. The novel vfeatures of` the `tone arm embrace construction which. permits quick detachment of the tonearinfrom a phono- Ygraph with sinfiu'ltaneousl disconnect of the vtransducer conductors. The construction also `provides static vertical balance of the arm to permit playing of recordsthat are .tilted Vand :inherently providing frictionless non-vibratory vertical pivoting and adjustment means for applying predeterminedneedle pressure. Provision is also made for a mute switch which is automatic in its operation when the tone arm is raised and lowered for playing.

These and other long sought features and advantages are absent in tone arms previous to this invention.

The principal object of the invention is the provision of a spring mounted balanced tone arm which may be quickly removed and replaced for needle and/or transducer substitution.

Another object of the invention is the provision of adjustment means for varying the vertical force supplied to the needle for playing.

Another object of the invention is the provision of a spring suspension for minimizing the transmission of transient vibration to the tone arm through its support.

A further object of the invention includes switch means for automatically short circuiting the transducer when the arm is moved toward its inoperative rest position.

These and other objects and advantages in one embodiment of the invention are shown and described in the following specification and drawing in which:

Fig. 1 is a side elevation of the arm in playing position with a portion shown in cross section;

Fig. 2 is a side elevation of the tone arm in rest position showing a cross section dierent than shown in Fig. 1;

Fig. 3 is a cross sectional end view of the arm taken through section line 3-3 Fig. 1;

Fig. 4 is a cross sectional end View of the arm taken through section line 4-4 Fig. 1;

Fig. 5 is an enlarged perspective View showing a fragmentary portion of the tone arm disconnected from its support.

Referring to Fig. 1 the tone arm I made from insulating material is supported by vertical spindle 2 which spindle is adapted to be raised, lowered and rotated by means not shown. In the position shown, the needle 3 secured in transducer 4 is in playing contact with record 5. A socket 3 member '6 is adjustably retained 'on the upper `end of spindle 2 by screw?. A counter-weight t secured tothe rear portion of the tone arm is pro- `-portioned to vertically balance the weight of the 'forward-end of the tone-farm about Vaxis c-a.

Referring to Fig. 5 Vthe socket member `6 is made Afrominsulating `material and contains two conventional ktip jacks f`il spaced asshown. .A pair of Asprings IU-ill are secured at onefend -to the tone -arm by individual laterally spaced `screws lIlI-I I` shown Figs. `1` and 4. Apair of plugtips l'I2-I2 are` `secured in opposite ends of springs Ill-II) and bridged by insulator I3 retained as shown by tips I 2. The spacing of tips i2 is identical to the spacing of the jacks 9-9. A shoulder screw I 4 shown in Figs. 2 and 4 threaded through the tone arm projects through a hole in insulator I5 which straddles springs I0. Since the springs I -I 0 are normally biased upward, it is apparent that the screw Id may be adjusted to vary the normal tension of both springs I to adjust the vertical pressure on needle 3. A stop member I6 secured to the tone arm normally projects through the space between the two springs It and under the insulator I3. This stop member prevents the springs from being over-stressed in an upward direction when the tone arm is removed by upward force sufficient to disengage the tips I2 from the jacks 9. A T-shaped mute blade I l is retained to the tone arm under stop I6 and is positioned in the path of movement or the upper ends of the tips I2-I2. Thus, when the mute blade I l is resting on the tips I2, a short circuit is applied to the transducer which is normally connected by conductors to the lugs I8 I8 of the springs I6 respectively. The tip jacks 9-9 are normally connected to individual conductors for transmitting the output of the transducer to an amplifier. In operation and referring to Fig. 2, the elements of the tone arm are shown in their normal rest position with the needle 3 disengaged from `the record 5 and the mute blade i 'l resting on the upper ends of tips I2 by virtue of the tilting tension in springs I0. Thus when spindle 2 is in its rest position, the needle is held away from the record and the blade Il applies a short circuit to the transducer.

When the spindle 2 is lowered to a predetermined position, the needle 3 will engage the record 5 and the tone arm will tilt vertically substantially about axis at right angles to (a) and the blade Il will move upward away from contact with pins I2 and permit the output of the transducer to be transmitted through the tip jacks il to an amplier not shown, and the tone arm is free to undulate in a vertical direction with a substantially constant needle pressure, by virtue of the resilience in springs Ill-l0.

It is to be noted that since the forward end of the tone arm is intended to be balanced by the counterweight 8, there will be no inertia force present tending to dislodge the needle from the record in a lateral direction due to a tilted position of the phonograph. It is also apparent that because of the resilient nature of the springs lll-l that transient vibration in the spindle 2 will be absorbed through springs I0 and not be transmitted to the transducer, thus eliminating distortion in the output thereof.

It is also apparent that the tone arm may be quickly removed by lifting the arm in a vertical direction and disengaging tips I2 from the tip jacks 9.

Having described my invention, I claim:

A quick detachable tone arm comprising an arm with a transducer secured in one end for playing phonograph records, said arm statically balanced about a horizontal axis, a vertical shaft adapted for predetermined movements along its axis, a socket support secured to the upper end of said shaft, a pair of electrically independent sockets in said support adapted to be connected to a pair of output conductors, a pair of electrically independent flat springs secured at one end in parallel spaced relation in said arm and positioned substantially parallel thereto, each of said springs having a pin secured in its free 4. end and positioned normal thereto for holding engagement in each of said sockets respectively, a pair of conductors connecting said springs to said transducer for completing a circuit to said sockets, said springs formed to normally bias the transducer of said arm in a downward direction, a substantially flat mute blade secured in said arm above said springs and positioned to contact and short circuit said springs when said arm is in rest position, whereby the downward movement of said shaft a predetermined distance will engage said transducer with a record and pivot said arm about said horizontal axis against the tension of said springs to release contact of said mute blade against said springs and apply Y a predetermined pressure of said transducer against said record.

References Cited in the file 0f this patent UNITED STATES PATENTS Number Name Date 1,891,369 Curtis Dec. 20, 1932 2,331,122 Jones Oct. 5, 1943 2,356,467 Martin Aug. 22, 1944 2,368,198 Brown Jan. 30, 1945 2,446,324 Di Ghilin Aug. 3, 1948 2,557,752 Miner June 19, 1951 FOREIGN PATENTS Number Country Date 307,091 Great Britain Feb. 27, 1929

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