US1743071A - Sound receiver - Google Patents

Description

Jan. 7, 1930. HAYES 1,743,071

S OUND RECEIVER Filed Aug. 17, 1927 avweutoz Herve C. H y $51 @Mom Patented Jan. 7, 1930 PATENT OFFICE HARVEY o. Earns,

OF WASHINGTON, DISTRICT OF COLUMBIA SOUND RECEIVER Application filed August 17, 1927. Serial No. 213,633.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 30, 1928; 370 0. G. 757) in the use of microphones where great accuracy and uniformity of operation is required,

as in the case of binaural reception. An important feature of devices to be used in such work is the ability to match them and this quality is not present in the usual microphones. It is not only diflicult to match microphones but they rarely remain matched for any length of time even when properly matched at the outset. Various types of magneto-electric devices commonly known as magnetophones, have been employed as substitutes for microphones where extreme sensitivityis not required, and with the improved construction of amplifier tubes, furthermore, the need for such great sensitivity no longer exists in the majority of cases. I

Magnetophones heretofore employed for the reception of sound, however, have had certain inherent difiiculties which the present "nvention has sought to overcome. For example, the usual types of magnetophone heretofore known, do not create distortionless sound receivers mainly for two reasons. First of all, the eddy current and hysteresis losses in the iron commonly employed in the cores and armatures of these devices. vary with the frequency of the electrical oscillations set up.

In the second place, the variation of the reluctance of a magnetic circuit which has heretofore been commonly relied upon to produce electrical effects corresponding to the sound or similar waves received, has a hyperbolic instead of a linear relation with respect to the motion of an armature or similar device which is moved to vary the reluctance in responseto the waves being detected. For faithful sound reception, therefore, the flux of the magnetic circuit should be kept constant and the portions of the electrical circuits that carry the fluctuating induced current should have no enclosed iron. It is contemplated by the present invention to provide a magnetophone embracing these principles and overcoming the inherent difficulties in the previously known devices. In attaining the desired results the present invention, furthermore, provides a detector which is extremely simple and one in which only relatively few parts, all having a constant definite relation to each other, are required. There are no loose parts or particles in the device contemplated which mayl become displaced and remain so to vary t e effects produced.

The present improvements, furthermore, involve only extremely light moving parts so that their natural frequency may be made relatively high Without requiring large forces to displace them and thereby destroying the sensitivity of the device. In this way, it is possible to tune the device to a natural frequency which is considerably above the range of frequencies to be detected. Accurate reception requires a natural frequency outside of the sound spectrum to be received since both the intensity and phase relation of the effects produced upon a sound receiver change rapidly near the resonance frequency.

An incidental object produce an electric current having a relatively high E. M. F. which is particularly suited for amplification. With these and other incidental objects in view, one suitable form of embodiment of the invention may be 5 particularly described with reference to the drawings in which 1 Figure 1 is a plan view of the improved magnetophone, and

Figure 2 is a sectional view along a diam- 9o eter line of Figure 1.

An electro-magnet, having a U-shaped core (1) formed of any suitable material, preferably laminated transformer steel is provided I on each leg with a coil (2). Current from a. D. C. source 2 is passed through the turns of the coils in such sense as to establish op-' posite poles at the ends of the U For this purpose the coils may be connected together either in series, as shown, or in parallel. Pole of the invention is to 80 y is formed as a loop,

. conductor (6),

will be passed into pieces (3) are provided at the ends of the core and are turned toward each other so as to provide a relatively small air gap between them. Secured by any suitable means in a position adjacent to the pole pieces (3) is an annular ring 4) which may be in the form of a disc having a hole at its center in line with the air gap between the pole pieces. A radial slot 5) serves to split the ring and provide an air gap or break in the circuit between the ends thus formed. If: desired, this gap may be filled by any suitable non-conductor of electricity. The ring or disc itself is preferably formed of non-magnetic material which is a good conductor of electricity. A conductor (6), preferably made of-aluminum or copper, or other good conductor of electricity, and relatively light in weight, the ends (7) and (8) of which are secured in any suitable way to the ring (4) at opposite sides of the slot or nonconducting portion (5). The mid-portion of the loop is bent up slightly as shown and is passed through the air gap between the pole pieces (3). A rod (9) connected to the member (6) at substantially its mid-point, is attached at its other end to some sound receiving device, such as the diaphragm; (10). A coil (11) having a relatively large number of turns of insulated wire is mounted in a groove in the periphery of the ring or disc (4). Preferably the groove will be lined with some insulating material such as indicated by the numeral (12). The operation of the device is as follows:

When a sound or similar Wave strikes the diaphragm (10), the motion of the latter will be transmitted by the connector (9) to the which will thus be oscillated in the magnetic field between the poles (3) of the electro-magnet. The cutting of the lines of force thus brought about will serve to induce a current in the conductor (6) and this the ring (4) as by means of the contact (7), and'after traversing the ring will be returned the contact 8) The air gap,or insulated portion (5) will insure that the alternating current that is induced will traverse substantially the entire circumference of the ring. Since the latter is of relatively large cross section, the current induced therein, due to the movements of the conductor (6), will be comparatively large but of correspondingly low E. M. F. The current flowing in the ring will induce a corresponding current in the coil (11) which becomes the secondary of a transformer and due to the large number of turns in this coil the E. M. F. produced at its terminals will be relatively high while the current will be comparatively small. This is the type of current which is best suited for amplification so that the terminals of the coil may readily be directly connected to the input terminals"! 13) of an amplifying unit 1 through to the conductor through electrical "claims appended. It will be noted that the construction disclosed serves to avoid the two previously mentioned difficulties inherent in similar devices previously known, thus there is no enclosed iron within the circuit of the sound actuated armature (6) and the magnetic flux between the pole pieces (3) is maintained constant throughout.

The invention herein described may be manufactured and used by or for the Government of the United States for governmental purposes without the payment tome of any royalty thereon or therefor.

What I claimis:

1. In a sound detector an electro-magnet having a relatively small air gap provided between the poles thereof, an annular member of good electrical conductivity, said member having a radial slot therein, an armature having its ends connected to said member adj acent opposite sides of said slot the mid-portion of said armature being oscillatable in the air gap between said poles, means for oscillating said armature in accordance with the sound waves to be detected, and a coil "mounted on said member adapted tohave a current induced therein in accordance with the movements of said armature.

2. In a vibration detector an electro-magnet having its poles so arranged as to form a small air gap, an electrical conductor passing said air gap substantially mid-way between said poles, a second relatively large electrical conductor connected at opposite ends to said first conductor, a coil mounted on said second conductor, and means for vibrating said first mentioned conductor in accordance with the vibration to be detected whereby a current will be induced in said coil.

3. A device for generating electrical impulses comprising a magnet,' a split ring, an

conductor having its ends connected to said ring and having an intermediate portion passing through the field of said magnet, a coil mounted on saidring, said coil having its turns concentric with said ring, and means for vibrating said intermediate portion of said conductor thereby inducing a current in said coil.

4. A device for generating electrical im pulses of relatively high potential compris ing a split ring, a coil mounted on said ring,

I so

' said coil having its turns concentric with respect to said ring, and means for inducing a current of low potential in said ring whereby a relatively high potential is created in said 5. A vibration detector comprising a magnet, a split ring of good electrical conductivity adjacent said magnet, a coil mounted on said ring, an electrical conductor connected to said ring, and means responsive to the vibration to be detected'for moving a portion of said conductor across the field of said magnet.

6. A vibration detector comprising an electro-magnet having its poles in close prox imity, a disc of good electrical conductivity arranged adjacent said magnet poles, said disc having an openin at its center and a radial slot extending rom said opening to the periphery of said disc, a coil mounted in the periphery of said disc, a conductor having its ends attached to said disc at opposite sides of said slot, and means passing through the opening in said disc adapted to vibrate a portion of said conductor in the field of said magnet in response to the vibrations being detected.

7 In a device of the class described, a magnet, a ring of non-magnetic material adjacent the poles of said magnet, means connected to said ring and movable across the field of said magnet to induce a current in said ring, and a coil in inductive relation with respect to said ring.

8. In a device of the class described, an electro-magnet, a disc of non-magnetic material mounted in contact with the poles of said magnet, said disc having a radial slot and a central aperture formed therein, a light electrical conductor having its ends secured to said disc at opposite sides of said slot, means for moving a portion of said conductor across the field between the poles of said magnet and a coil in inductive relation with respect to said disc.

9. In a device of the class described, a magnet, a coil mounted adjacent said magnet, and an electrical conductor mova'ble in the field of said magnet and adapted upon movement to induce currents in said coil, said coil being so mounted as not to enclose any magnetic material.

10. In a device of the class described, a magnet adapted to establish a constant flux, a coil mounted adjacent said magnet, and an electrical conductor movable in the field of said magnet and adapted upon movement to set up induced currents in said coil, said conductor being so arranged as not to completely surround any magnetic material.

HARVEY C. HAYES.

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