US1823162A

US1823162A - Electrical reproduction of sound from records

Info

Publication number: US1823162A
Application number: US427764A
Authority: US
Inventors: Pearson Laurence Herbert; Marshall Claude
Original assignee: Individual
Current assignee: Individual
Priority date: 1930-02-12
Filing date: 1930-02-12
Publication date: 1931-09-15
Anticipated expiration: 1948-09-15

Description

ELECTRICAL REPRODUCTION OF SOUND FROM RECORDS Filed Feb. l2, 1930 2 Sheets-S1186?I l Sept. 15, 1931. H. PEARsoN ET AL ELECTRICAL REPRODUCTION OF SOUND FROM RECORDS 2 Sheets-Sheet 2 Filed Feb. l2. 1930 Patented Sept. 15, 1931 UNITED STATES :Parar Fries iIITJLIIC'JRICALV REPRODUCTION Ol" SOUND FBQLVI` RECORDS M' i Application led February 12, 1830. Serial No. 427,764.

This invention comprises improvements in or relating to electrical reproduction of sound from records and has reference to apparatus for use in the electrical transmission 5 of music, speech and other sounds from graniophone records.

In connection with apparatus of this class an electrical device known as a pick up or collector is employed, adapted for attachi0 ment to the tone arm of a gramophone and embodying a metal reed resiliently or pivotally mounted or suspended so as to be capable of a limited oscillatory movement between the poles of an electromagnet. Detachably carried by the reed is aneedle adapted to coact with the gramophone records in the known manner so that the vibration set up in said needle and reed by the irregularities in the record surface induce in 'Q0 the pole coils of the magnet varying electric impulses which are suitably amplified and conveyed to a loud speaker such as is used with wireless receiving instruments, or other reproducing instrument.

'g5 In order faithfully to reproduce the music, speech or the like in the loud speaker and prevent distortion it is essential that the reed and needle be normally held from uncontrolled movement `while permitting the '30 oscillatory motion effected by the record, and to this end it is the custom to damp the lateral motion of said reed and needle between adjustable resilient damping-elements i or cushions.

35 The present invention has reference to the type of pick up comprising a permanent magnet of the horseshoe type having coil carrying pole tips associated with each limb and having a metal reed resiliently mounted o at its upper part and positioned between said pole tips and adapted to be oscillated to a limited extent bythe needle traversing the grooves of the gramophone record tok induce electric currents in the coils of the mag- '45 net, aspreviously described.

According to the present invention a pick -up or collector is provided embodying inl -combination a permanent horseshoe mag net, a coil on each pole piece or tip of said to magnet, a resiliently mounted metal reed between said' pole coils, the length of said caf reed approximating the diameter of the pole coils, adjustable reed damping means eX- tending through the pole tips and means for adjustably locking said damping means inet? position relatively to the reed.

A further feature consists in mounting the pick-up upon a hinged or pivoted tone arm which is provided with counter balancing means, the balance of the tone arm being 1ST 5 advantageously adjustable.

For the purpose of more fully describing the nature of this invention reference will now be made to the accompanying drawings, wherein zt (i3 Figure l shows in part sectional elevation a pick-up or collector in accordance with this invention.

Figure 2 is a rear view of the device shown in Figure 1. A'170 Figure 3 is a part sectional lside elevation of a modiied construction of pick-up mounted upon a counter balanced tone arm, said arm having associated therewith means for adjusting the balance thereof.

Figure 4 is an enlarged sectional elevation of a modified construction of pick-up shown Y in Figure 3;

Figure 5 is a front view looking in the direction of arrow X in Figure l. S0 ln one method of carrying Aout the invenn tion the pick up or collector comprises a permanent magnet l of horseshoe formation having coils 2 wound on pole tips la one of which projects inwardly from each limb of 85 the magnet. On an insulating bar 3 extendving across the magnet are a pair of terminals 4 for the'coil windings,.and the induced currents from said terminals are suitably amplified and conveyed to a suitable reproducing instrument such asa loud speaker. A split metal socket 5 is provided at the one side of the device for attachment to the tone arm of a gramophone.

Dependinglbetween the pole tips laris a Ametal reed 7, preferably of rectangular cross section, suitably anchored to a `member 6. This member 6 is rigidly connected by a screw 6a and nut 6?) to a back plate 1b which 100 may be screwed to the rear of the -inagnetl and shaped at its upper edge to conform to the curvature of the said magnet. Advantageously the fixing of the reed is approximately midway in the height of the magnet.

The reed is bored vertically at its lower or free end to receive a gramophone needle 8, which latter is detachably fixed in position so as to projectdownwardly by a screw 9 inserted laterally into a threaded hole in the reed.

The needle fixing screw 9 is preferably a thumb screw and the length of same is such that the screw head projects out clear of the magnet coils 2 and can be manipulated with ease by the fingers without touching the coils.

The pole tips 1a upon which the magnet` coils 2 are mounted are of tubular formation and each may be adjustably fixed in position by a screw 10 which is inserted through a plain hole in the magnet end portions 1c and into an internally threaded part of the bore of the pole piece. Each pole tip projects inwardly beyond the coil 2 and the innermost half or part of the bore .is preferably of increased diameter so as to accommodate a loose metal piece 11 and a small piece of rubber 12 or equivalent non-conductive resilient material.

This rubber element 12 projects a little way beyond the inner face of pole piece la, and it will be appreciated that the two rubber elements located one on each side of the reed 7 constitute dampers functioning normally to hold said reed centrally between the magnet poles and preventing promiscuous lateral movement of the reed.

The aforesaid screws 10 are hollow, and within each of said screws is a further screw 13 bearing at its inner end on the loose metal piece 11. The axial adjustment of this inner screw 13 effects an adjustment of the said loose piece 11 and damper 12, and also determines the degree of pressure exerted by said damper on the reed.

The screw 13 is locked in its adjusted position by nut 14.

The dampers being located substantially near to the fulcrum of the reed provides for a maximum amount of leverage of the associated reed and needle and ensures a particularly sensitive operation thereof when operating upon a gramophone record, thus producing exceptionally accurate and clearly defined results in the loud speaker.

In a modified arrangement illustrated in Figures 3 to 5 the horseshoe magnet v1 is mounted upon a back plate 15 which has cast integrally therewith a boss 16 by which the pick up is suitably connected to the tone .arm 17. Y Y

In this arrangement the pole pieces 1a instead of being connected directly to the limbs of the magnet 1, are mounted upon angle bracket members 18 which are fixed to the rear plate 15 so that one fla-nge of each angle member projects outwardly and forwardly from said rear plate. The twoV limbs of the magnet bear upon the upstanding flanges of the angle members 18, said magnet being secured in position by an insulated or nonmagnetic cross bar 3 which extends across the front of the magnet and is connected to the rear plate 15 by a screw, bolt or the like 19. The screw member 19 which is located centrally in the width of the pick up also serves as a means for connecting the reed 7, said reed advantageously depending from a member 20 which also functions as a spacing sleeve between the bar 3 and back plate 15. On the plate 15 is also suitably fixed an insulating block or member 21 carrying a pair of terminals 22 to which wire extends from Vthe two coil windings 2 mounted on the pole pieces of the magnet.

Damping means for the reed are provided as hereinbefore described said damping means beingadjustable by screw adjustment also as before-described. In the modified arrangement, however, the screw adjustment for the reed damping means is passed through the upstanding flange of each angle member 18 instead of, as in the first described embodiment, through each limb of the magnet.

By reasonof the fact that the adjustment, of the reed damping is effected axially of the pole pieces, the size and weight of the actual reed or armature carrying the needle are reduced to a minimum, and the efliciency of the device consequently enhanced.

The tone arm 17 is preferably pivoted org" hingedto the upper end of a screwed spindle member 23 (Figure 3) said spindle being adapted to rotate within an internally threaded pillar 24, said tone arm having an,

enlarged portion 25 overhanging a pivot 26 so as to constitute a counter balance for the pick up.

Advantageously the overhanging portion 25 of the arm is made hollow and accommo-` dates a weight`27 carried by screw-threaded`Alv pin 28 passing through a threaded aperture in the end of said portion 25, the arrangement being such that by rotation of the pin 28 and weight 27 thereon the position of said* weight relatively to the pivot 26 can be adjusted'and by so doing the balance of the tone arm can be adjusted to the exact required degree. A milled knob 29 is provided at the end of the screwed pin 28 for the manipulation thereof, a fixing nut 30 being advantageously also provided for fixing the weight 27 at the adjusted position.

Weclaim 1. A pick up for the electrical reproduction of sound from records, embodying in combination a permanent horseshoe magnet having hollow cylindrical pole pieces, said pole pieces being mounted on bracket members'positioned adjacent'to the two limbs of the magnet, a coil on each pole piece, a metal reed resiliently suspended between the coils, the length of said reed approximating the diameter of the coils, a screw operating axially within each pole piece, cushion elements for damping the reed located on each side of said reed and said screws functioning adjustably to determine the position of said cushions.

2. A pick up for the electrical reproduction of sound from records, embodying in combination a. permanent horseshoe magnet, a plate on which said magnet is mounted, said plate being adapted for connection to a tone arm, bracket elements mounted on said rear plate adjacent to the two limbs of the magnet, hollow pole pieces on said brackets, a coil on each pole piece, a reed resiliently suspended between said coils, reed damping cushions, and said cushions being adjustable by screws located and operating axially of said pole pieces and coils.

3. A pick up Jfor the electrical reproduc tion of sound from records, embodying in combination a permanent horseshoe magnet, a rear plate carrying said magnet, said rear plate being connected to a tone arm, an angle bracket fixed to said rear plate adja cent te each pole of the magnet, an externally and internally threaded sleeve screwed through an upstanding part of such bracket, a hollow cylindrical pole piece carried by each sleeve, a coil on each pole piece, a metal reed suspended resiliently between said pole coils, means for detachably iixing aneedle to said reed, a damping cushion element on each side of said reed and a screw member located axially of each coil and operating within each sleeve adjustably to determine the position of the damping elements relatively to said reed.

A. The combination claimed in claim 3 wherein the pick up is carried by a hinged tone arm which is provided with counter balancing means.

5. The combination claimed in claim 3 wherein the pick up is carried by a hinged tone arm having counter balancing means which are adjustable to adjust the balance of the arm.

LAURENCE HERBERT PEARSON.

CLAUDE MARSHALL.