US1875848A - Nonvibratory mounting for reproducer arms - Google Patents

Description

Sept. 6, 1932. c T 1,875,848

NONVIBRATORY MOUNTING FOR REPRODUCER ARMS Filed May 19, 1930 INVENTOR Patented Sept. 6, 1932 noun 0. near, or rasanana g catmoama HONVIBBATOBY MOUNTING FOB REPRODUOER ARMS Application fled Kay 10, mo. Serial in. 453,575.

This invention relates fgenerally to sound reproducing apparatus the type utilizing mechanical disk records, and is more particularly concerned with a vibration absorbing mounting for the swinging arm which carries the reproducer pick-up unit in such apparatus.

Sound reproducing apparatus is designed with a particular view toward reducing mechanical vibrations to an absolute minimum, as such vibrations when transmitted to the ick-u unit introduce serious distortions and irregu arities in sound reproduction. It has been found to be an extremely diflicult prob- 15 lem, however, to so balance and cushion the apparatus that all such vibrations are effectively eliminated.

It is the prima object of the present invention to provi e a vibration. absorbing mounting for the arm which carries the reproducer pick-up unit, so that thepick-up unit will be eflectively insulated from all of the vibrations in the other parts of the apparatus.

25 According to the present invention, the reproducer arm is provided at its rear end with a resilient, vibration-absorbing mounting on the frame of the ap aratus, which effectively insulates the reproducer arm from all of the 30 usual vibrations encountered in the normal operation of the apparatus. The invention itself will best be understood from the following detailed description of a present preferred embodiment thereof, ref- 35 erence' for this purpose being had to the accompanying drawing, in which:

Fig. 1 is, a perspective view of a ty ical record table showing the application 0 my improved reproducer arm mounting;

Fig. 2 is a vertical section taken on line 22 of Fig. 1;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 2;

Fig. 4 is a section taken on line 44 of 45 Fig. 2; and

Fig. 5 is a horizontal section taken on line 55 of Fig. 2, parts being broken away to show in section.

Referring now to the drawing, the numeral 50 indicates a record table, driven in any usual manner, and upon which is supported and centered a phonograph record 11. 'Extendlng from a frame part 12, from which the record table 10 is supported, is a bracket 14 which carries at its outer end the reproducer unit generally indicated by the numeral Reproducer unit 15 embodies inthe present instance a tubular arm 16 carrying at its free forward end a pick-up unit of usual constructlon, a'nd pivotally and resiliently mounted at its rear end, as now to be described, upon the outer end of bracket 14.

The outer end of bracket 14 supports a base member 20 for the reproducer mounting, which member is positioned on bracket 14 by means of a pin 21 fitted thereinto, and which carries a vertical tube 22 into which is fitted a rubber cushion 23 for the mounting of the reproducer arm. Cushion 23 carries a coaxial bearing sleeve 25 for the pivot pin 26 of the reproducer arm supporting frame 28, frame 28 being vertically supported by means of its shoulder 29 which rests on the upper end of sleeve 25.

Frame 28 has in the present embodiment, two oppositely extending arms 30 carrying at their outer ends rings 31, which rings are disposed with their axis horizontal and parallel. A coil spring 33 is secured at its outer end within each of the rings 31.

The rear end of tube 16 carries a yoke 36 embodying a pair of oppositely extending arms 37, which arms are secured at their outer ends to the inner ends of coil springs 33. For this purpose the inner ends of springs 33 may be soldered or otherwise secured to the shank of a headed screw 40 carried by the ends of yoke arms 37, as clearly shown in Figs. 4 and 5. The inner portion of each spring is confinedbetween washers 41 and 42 on screw 40, while a soft rubber disk or cushion 43 is provided outside of washer 41, the whole assembly being held together by a nut 44 on the end of screw 40.

The leads from the pick-up unit preferably pass through the tubular arm 16, as shown, so that they will not drag over the surface of the record.

The reproducer arm is free to pivot at its rear end to allow its pick-up unit to follow the record groove by rotation of pin 26 in bearing sleeve; and the coil springs 33 allow the arm to be raised to lift the pick-up unit off the record. When the reproducer arm is not in use it is supported by a rest 56 carried by the base member 20 of the mounting.

The rubber cushion 23 in which the supporting pin 26 of the mounting is carried aids in insulating the reproducer unit from the vibrations of the supporting bracket 14. The chief vibration-absorbing element, however, is the resilient spring-support of the reproducer arm, which is of sufficientflexibility to absorb every perceptible vibration of the supporting bracket arising in normal operation and, except for any unusual movements of the apparatus, supports the reproducer arm and pick-up unit in substantially perfect steadiness.

Thus, since the reproducer arm is carried by the centers of the coil springs, the usual vibrations in the apparatus may cause the outer ends of the springs to be correspondingly vibrated in an axial direction, that is, longitudinally of the reproducer arm, andalso to be correspondingly vibrated laterally in any direction, without such vibrations being transmitted through the springs with suf ficient energy to overcome the inertia of the reproducer arm and the pickup unit sufficiently to set up the slightest perceptible vibrations thereof.

The drag of the record on the pick-up unit tends to stretcher extend the coil springs forwardly, as illustrated in Fig. 5,and especi ally is this effect noticeable at the lower frequencies. To. curtail this effect the rubber cushions or disks 43 are provided, which resiliently contact the back edges of rings 31 and thereby prevent more than an allowable extensionof the springs. The resiliency of the rubber disks, however, similarly to that of the coil springs, cause them likewise to absorb vibrations of the reproducer mounting and to prevent their transmission to the pick-up unit.

- It will be understood the drawing and description are to be considered merely as illustrative of and. not restrictive on the broader claims appended hereto, for various changes in design, structure and arrangement may be made without departing from the spirit and scope of said claims.

I claim 1. In sound reproducing apparatus, the combination of a frame adapted for support of a rotatable record table,'a reproducer arm, a mounting for said reproducer arm on said frame, and a vibration absorbing unit included in the mount ng of said reproducer arm; said mounting including a member pivoted to said frame, a pair of coil springs each supported at one end of its coil by said memher, said coils being relatively disposed with idly connected at one of its ends to their axes parallel and in spaced relation, a.

reproducer arm extending parallel to said coil axes, and a supporting connection between the opposite end of each of said coil springs and said reproducer arm, said connection ineluding a cushion adapted resiliently to limit extension of said spring.

2. In sound reproducing apparatus having a frame adapted to support a record table, areproducer arm, and a coiled spring connected at spaced points in its length with the frame and reproducer arm and forming the sole support of the arm on the frame, said spring eing resiliently yielding in all directions.

3. In sound reproducing apparatus having a frame adapted to support a record table a reproducer arm, and a resilient yielding member connected between the reproducer arm and the frame and forming the sole support of the arm on the frame, said yielding for rotation on a vertical axis, the combina tion of a supporting member pivoted with respect to said frame on an axis parallel'to the table axis, a 0011 spring connected at one end to said supporting member, and arranged with its axis in a plane substantially at right angles to said table axis, and a reproducer arm connected for its support to the other end of said coil spring and extending substantially in the direction of said coil axis.

5. In sound reproducing apparatus having a frame adapted to support a record table for rotation on a vertical axis, the combination of asupporting member pivoted with respect to said frame on an axis parallel to the table axis, a pair of coil springs each rigsaid supporting member, said coil springs arranged with their axes parallel and extending in planes substantially at right angles to the tale axis, and a reproducer arm connected for its support at its rear end to the free ends of said coil springs and extending substantially parallel to the axes of said springs.

6. In sound reproducing apparatus having a frame adapted to support a record table for rotation on a vertical axis, the combination of a supporting member pivoted with respect to said frame on an axis parallel to the table axis, a spirally coiled spring connected at its outer end to said supporting member and arranged with its axis in a plane substantially at right angles to the table axis, and a reproducer connected for its support to the free inner end of said coil spring.

In witness that I claim the foregoing I have hereunto subscribed my name this 24 day of April, 1930.

ROBERT C. BURT.

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