US2555936A

US2555936A - Electromagnetic reed unit for electrical musical instruments

Info

Publication number: US2555936A
Application number: US11066A
Authority: US
Inventors: Harold E Rogers; John M Magida
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-02-26
Filing date: 1948-02-26
Publication date: 1951-06-05
Anticipated expiration: 1968-06-05

Description

l`lune 5, 1951 l A/n H ow H. E. ROGERS E' AL ELECTROMAGNETIC REED UNIT FOR ELECTRICAL MUSICAL INSTRUMENTS Filed Feb; 26, 1948 Fig. 2.

a "III'IIIIIA'IIIIIL l i /9 /5/4 l0 20 A L /q Fig. 5.

\ l0 Haro/d E.- Rogers L ,6 John M. Mag/da INVE'NTOR- Patented June 5, 1951 ELECTROMAGNETIC REED UNIT FOR ELEC- TRICAL MUSICAL INSTRUMENTS Harold E. Rogers. Los Angeles, and John M. Magida, North Hollywood, Calif.

Application February 26, 1948, Serial No. 11,066

Claims.

This invention relates to electrical musical instruments using steel reeds for producing musical tones and it has particular reference to the translation of the mechanical oscillations of the steel reed into electrical oscillations.

The main object of the invention is to provide an improved translation unit, which is simple, effective .and compact and which improves markedly the quality of the tone obtainable by retranslation of the electrical oscillation into sound waves.

A further object of the invention consists in eliminating from electrical reproduction all external influences, not manifesting themselves in the oscillations of the reed itself and due partly to the method of starting the oscillations by means of an air current and partly to disturbances in the Vicinity of the reed, so that the waves of the electrical currents produced represent solely the fundamental oscillation of the reed and their harmonics.

A further object of the invention consists in making the oscillations of a reed most effective for faithful current production by using a magnetized reed, oscillating in the interior of a coil.

A further object of the invention consists in rendering the oscillations of the reed most effective for faithful current production by arranging a ilat reed inside of a coil consisting of windings which are arranged in substantial parallelism to the plane of the flat reed on both sides of the same.

A further object of the invention consists in rendering the oscillations of the reed most effective for current production and in securing a high delity of reproduction by using a ilat reed arranged on the inside of a coil in a plane approximately bisecting the height of the coil with the windings arranged in planes parallel to the plane of the reed.

A further object of the invention consists in providing a compact unit of high eiciency by using an insulating frame closely surrounding the oscillating reed having walls reduced to a minimum around the end of the reed.

Further more specific objects will be apparent from the detailed specication.

In known electrical instruments using vibrating reeds for producing musical tones of a desired pitch, quality, timbre or other characteristics, musical tones are customarily produced by blowing air against oscillating reeds. The mechanical oscillations of the reed produce an air vibration manifesting itself as a tone which is then translated into electrical oscillations by some electroacoustic means such as a microphone. In most cases, however, this tone is at least partly contaminated by undesirable noises produced by the rushing air blowing against the reeds and .also by the control mechanism of the air jets such as keys, flaps, valves, etc. which all produce sounds upon being moved or upon coming to a stop.

It is therefore desirable that the electroacoustic apparatus be replaced for instance, by an electrostatic or electromagnetic translation apparatus. However devices of this type are mostly not satisfactory as they are selective .and do not furnish a perfect reproduction of the reed oscillations.

According to the invention an electromagnetic device is used which furnishes an approximately perfect translation of the natural reed vibration, comprising not only a fundamental oscillation, but also a number of overtones. The essence of the invention consists in placing a coil in a magnetic field produced by and surrounding the magnetized vibrating reed, the reed oscillations in this case changing the reluctance of the' path of the magnetic field of the magnetized reed. The change in the eld induces an oscillation in the coil corresponding exactly to the reed oscillation.

The inventive concept is best described by referring to the accompanying drawing showing one embodiment thereof. It is however to be understood that this particular embodiment is to be regarded as an example serving the purpose of explaining the principle of the invention and `a preferred mode in which it is contemplated applying this principle. The information supplied when describing this example will enable experts skilled in this art to construct further embodiments of the invention and modifications of the example described and sho-wn are therefore not necessarily departures from the invention.

In the drawing:

Figure l is a perspective sectional view of a unit according to the invention, on a much enlarged scale showing part of the unit broken away and a transverse section at the point where it is broken.

Figure 2 is a plan View of the unit.

Figure 3 is a sectional elevational View of the unit, the longitudinal section being taken `along line 3 3 in Figure 2.

Figure 4 is a sectional elevational View the section being taken along line 4-4 in Figure 2.

Figure is a sectional elevational view the section being taken along line 5-5 in Figure 2.

Figure 6 shows the direction of the air flow which is blown through the channel.

The unit according to the invention comprises the reed I0 which consists of magnetized steel and of a reed holder or carrier frame I2 of an approximately rectangular prismatic shape surrounding the reed completely and enclosing it between its walls. The reed is held in a plane coinciding with or adjacent to the median plane of symmetry bisecting the height of the open prismatic reed holder frame I2. I4 at one end of the frame I2 forms the base on which the reed is attached by means of a screw I5.

The outer walls of the prismatic reed holder frame are at and carry a coil 29 to be described below. The inner wall projects towards the reed vso as to surround .it very closely in the middle portion of the frame. The end portions of the 'frame are however elliptically gouged (at I8) so as to recede from the reeds, but near the edge of the reed a ledge I6 is projecting the upper surface of which is approximately coinciding with the reed surface.

The walls are made as thin as possible in order to reduce the distance between the magnetized reed I0 and the coil 20 as much as possible. The gouging of the end permits a further reduction of the end wall I9 near the tip of the reed, which has the largest amplitude.

The coil 20 surrounding the frame I2 is of fine insulated closely wound copper wire applied in one or more layers and the ends of the coil wire are fixed to two terminal posts 2 I, 22, arranged at one end of the frame I2 which are provided with means for making connection with the operative circuits. The number of turns of the coil must be so chosen that the desired amplitude of the electrical current results when the reed is brought to oscillation.

'I'he unit above described is located above a blow pipe (not shown) such as conventionally used having its orifice below the gouged end portion I8 of the frame. The air blown against the tip of the reed produces its oscillation.

In operation the reed is brought to oscillation by the stream of air blowing through the gouged end I8 of the frame I2 towards the reed closely surrounded by the ledge ifi. There is however a suiiciently wide path for the escape of the air when the reed is lifted thereby widening the gap between it and the ledge. The reed thus deflected starts its oscillation with its natural frequency determined by its free length. The oscillation of the reed produces a periodic variation of the reluctance of the path of the magnetic iield and the resulting variation of the magnetic flux vtraversing the coil induces an electric current in the coil which is inversely proportional to the ux density (in gauss) prevailing in the area between the edges of the reedand the inner coil surface and to the length of wire (in cm.)

This current is solely dependent on the movement of the reed and therefore solely reproduces the vibratory movement to which it is subjected. All external Sources of disturbance are therefore without influence and are eliminated from reproduction. The current, therefore, varies merely n accordance with the fundamental oscillation and its harmonics as produced by the reed.

The current is then amplied and reproduced in a speaker or a similar translating device in the conventional manner.

A cross piece The coil 20 of very fine insulated copper wire is wound evenly around the outer surface. However the coils on the reeds of shorter length, oscillating with higher frequency, are provided with a larger number of turns in order to increase their electrical output and also their inductance to obtain uniform electric characteristics in all the units of an instrument.

It will be clear that 'variations or changes relating to the unessential details will not in any way affect the essence of the invention.

Having described the invention, what is claimed as new is:

1. A unit for producing oscillatory electric currents corresponding to musical tones for use in electrical musical instruments, with a flat, elongated reed of magnetized ferro-magnetic material of a length corresponding to the tone to be produced, adapted to be set into oscillation by a current of air blown against it, comprising a prismatic frame of insulating material with a prismatic hollow interior space forming a channel encircling the `feed completely, one cross section of said channel being approximately lled by said reed, said channel being thus substantially subdivided into two compartments by the reed, while adapted to conduct the air in a direction at right angle to the said cross section, a coil of ne insulated wire consisting of windings surrounding said frarne and encircling the zone occupied by the reed, said windings engendering cuirents upon variations of the magnetic eld produced by the oscillation of the reed in the interior or the coil.

2. A unit'for producing oscillatory electric currents corresponding to musical tones for use in electrical musical instruments, with a thin, ilat elongated, freely oscillating reed of magnetized ferro-magnetic material, of a free length corresponding to the frequency of the 'tone to be produced, adapted to be set into oscillation by a current of air blown against it, comprising a substantially prismatic frame of insulating material with a prismatic hollow interior space forming a channel encircling the reed completely, one cross section of the channel being approximately iilled by the reed, said channel being thus substantially subdivided into 'two compartments by the reed, while adapted to conduct the air in a direction at right angle to the cross section lled by the reed, said frame being provided with a stepped seat portion on its inner side, projecting into the interior of the elongated channel at one end thereof for xedly supporting one end of said reed, the walls of the frame projecting in wardly towards the reed being reduced to a minimum thickness in the portion surrounding the free end of the reed, a coil of fine insulated wire consisting or windings surrounding said frame and encircling the space occupied by the reed, said windings engendering currents upon variations of the magnetic field produced by the oscillation of the reed in the interior of the coil.

3. A unit for producing oscillatory electric currents corresponding to musical tones for use in electrical musical instruments, with a freely oscillating, thin, flat elongated reed of magnetized ferro-magnetic material of a free length corresponding to the frequency of the tone to be produced and adapted to be set into oscillation by a current of air blown against it, comprising a substantially prismatic frame of insulating material with a prismatic hollow interior space forming a channel encircling the reed closely and completely, one cross section of said channel being approximately lled by said reed, said channel being open for the passage of air through it in the direction at right angles to the plane of the cross section nlled by the reed, said elongated prismatic frame being provided with a stepped seat portion near one of its ends, forming' a seat for Xedly supporting the reed and being gouged above and below a middle zone close to the cross section filled by the said reed and near the freely oscillating end portion o1 the reed to reduce the thickness of the walls near said freely oscillating end portion of the reed, a coil of line insulated wire wound around the frame and consisting of windings arranged in planes substantially parallel to that of the reed, and further arranged above and below the reed so that the plane of the reed approximately bisects the height of the coil, said windings engendering currents upon variations of the magnetic eld or" the reed produced by its oscillation in the interior of the coil.

4. A unit for producing oscillatory currents corresponding to musical tones for use in elecrical instruments, comprising an elongated prismatic frame of substantially rectangular cross section, open at its ends and surrounding an elongated substantially rectangular hollow space forming an air conducting channel extending axially at right angles to the said cross section, a flat elongated reed of magnetized ferro-magnetic material substantially lling a cross sectional area of said channel and held for transverse free oscillation within said channel at a point intermediate between the open ends of the frame, a coil wound around said prismatic frame around the zone containing the cross section substantially lled by the reed, and means for producing free oscillations of said reed, within the interior of the coil, which in their turn produce currents within the coil exactly proportional to said oscillations.

5. A unit for producing oscillatory currents corresponding to musical tones for use in electrical musical instruments, comprising an elongated prismatic frame of substantially rectangular cross section open at its ends and surrounding an elongated substantially rectangular hollow space forming an air conducting channel extending axially at right angles to said cross section, a thin, Hat, elongated reed of magnetized ferromagnetic material of substantially rectangular shape, its length being a multiple or its width and the latter being a multiple of its thickness, the said reed being arranged within and approximately lling a cross sectional area of the said air conducting channel formed by the hollow interior of the prismatic frame, said reed being held in a position in which it is parallel to the basis of the prismatic frame, seating means on one end of said prismatic frame on the interior thereof, projecting into said hollow space at a point intermediate between the open ends oi said frame for xedly supporting one end of the reed, the projecting portion of the reed being free for oscillation within the channel, and a coil surrounding the said prismatic frame in the Zone in which the reed is supported, the reed thus oscillating Within the coil around a plane which is substantially perpendicular to the axis of the coil` HAROLD E. ROGERS. JOHN M. MAGIDA.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,026,342 Curtiss Dec. 31, 1935 2,119,584 Knoblaugh June 7, 1938 2,151,021 Frohman Mar. 2l, 1939 2,330,261 Beyer Sept, 28, 1943 2,383,553 Johnson Aug. 28, 1945