US1578285A - Sound box for talking machines - Google Patents

Description

March 30 1926. 1,578,285 M. A. HARDYMAN SOUND B oxIFoR TALKING MACHINES Filed April 11. 1922 f Ma Patented Mar. 30, 1 926. g

UNITED STATES I "1,578,285 PATENT OFFICE;

MAURICE.ARTI-IURHARDYMAN, OF CHARLTON, LONDON, ENGLAND, ASSIGNOR TO JOHN HARLINGBAILEY, OF LONDON, 'ENGLANDQ SOUND BOX FOB TALKING MACHINES.

Application filed April 11,1922. Serial No. 551,653.

To all whom it may concern. v

Be it known that I, MAURICE ART UR HARDYMAN, a subject of the King of England, residing at Charlton, London, England, haveinvented certain new and useful Improvements in Sound Boxes for Talking Machines, of which the following is a specification. 1

This invention is for improvements in or- According to this invention, such a soundbox is provided with a sound-chamber. be-

-' tween the back-plate and the tone arm socket, said chamber being of a diameter approximately equal to that of the operative portion of the diaphragm and, preferably, in-depth considerably deeper than the space between the back-plate and the diaphragm. The presence of-this chamber is found to result in a fuller tone which may be still further mellowed by constructing the chamber of non-resonant material, such, for example, as woo The front plate of the sound-box having a sound-chamber as described above, may have a small central perforation of diameter only such as is sufficient for the entrance and operation therein of the stylus-lever, instead of V the usual large opening, for the purposeof screening the diaphragm from external noises, such as arise from the scratching of the stylus upon the gramophone record.

In the accompanying drawings:

Figure 1 is a central vertical section through the sound-box at right-angles to the plane of the diaphragm;

Figure 2 is a plan of a diaphragm having a circular corrugation, and V Figure 3 is a section through the diaphragm shown in Figure 2 on the line 3-3 of that Figure. V

A diaphragm A is mounted between a back-plate B and cover-plate The cover plate C is cup-shaped and accommodates within it the diaphragm A and two spacing rings D. The back-plate-B provides a foun-f datlon upon which the diaphragm, sand-- wiched at itsiperiphery between the spacing rings D, is clamped by the plate C.

'hfounted on the back of the plate B concentrically with the diaphragm is a circular chambered member E of wood disposed with its open end towards the plate B. The other end of this chambered member is formed with a short tubular extension E in which is a tone-arm socket F. i The socket F has a circumferential flange F on its inner end which engages the inner face of the outer end of the chambered member E and through which it is screwed to said outer end. The internal diameter of the chambered member E is approximately equal to the diameter of the operative portion of the diaphragm A, and the interior depthfrom the back plate Bis approximately three times the depth of the space between the diaphragm and the back-plate. The back plate B has in it the usual central perforation B of diameter nearly equal tothat of the through-way of the tone-arm socket F,

The plate G'has a small central perforation 0 through which a stylus lever G opcrates; otherwise the plate C is imperforate. 1

The styluslever is mounted in the usual way on the exterior of the sound-box and is attached to the centre of the diaphragm.

In a preferred form of sound-box the diaphragm A is made of some mouldable' material such as sheet ebonite instead of the usual mica disc, and is formed'with one or more circular corrugations A as shown in Figures 2 and J f The ebonite may be of the class usually employed for electrical purposes and is preferably about 1/64th of an inch thick.

The corrugation A *is centrally disposed and lies near the periphery of the diaphragm but clearof. the spacing rings sound-box, so that it may flex freely with the operative portion of the diaphragm,

v The corrugation may be formed by ress-' ing the ebonite disc into a mould while 'ot.

By the employment of such a diaphragm, the tone is much improved compared'with that when the usualmica disc is used.

I claim 1. In a talking-machine sound-box, the

D when the diaphragm is in place in the combination of a diaphragm, aback-plate behindthe diaphragm having in itan opening for passage of sound emanating from the diaphragm, a tubular tone-arm socket Whose sound inlet is disposed opposite the opening in the back-plate, and a hollow cavity member of wood interposed between the back-plate end the tone-arm socket so asto provide a sound cavity behind the backplate and between it and the tonearm socket inlet, .the interior of which cavity inei'nber is so dimensioned that the cavity is greater in di ain-eter'than the opening in; the

"back-plate andthe inlet of the tone-arm socket and v greater indepth than the space behind the diaphragm having in it anopening for passage of sound emanating from the diaphragm, a tubular tone-arm socket Whose sound inlet is disposed opposite the opening in the back-plate, and 'a hollow cavity-member of woodinterposed between the backplate and the tone-arm socket so as to provide a sound cavity behind'the backplate and: between it and the tone-arm socket-inlet, the interior of which cavity member is so dimensioned that the cavity is substantially equal in diameter to the operative portion of the diaphragniand substantially equalin depth to three times the depth "of the space between the d-i-a e 'e i and thetaek-plate, substantially: described In. testimony whereof I aliix my signature.

MAURICE ARTHUR HARDYMIAN

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