US2494390A

US2494390A - Electrical pickup

Info

Publication number: US2494390A
Application number: US759367A
Authority: US
Inventors: Johnson Alfred
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-07-07
Filing date: 1947-07-07
Publication date: 1950-01-10
Anticipated expiration: 1967-01-10

Description

Jan. 10, 1950 A. JOHNSON 2,494,390

ELECTRICAL PICKUP Filed July '7, 1947 I N VEN TOR.

ATTD RN EYE Patented Jan. 10, 195

UNITED STATES PATENT OFFICE 4 Claims.

The present invention relates to electromagnetic pickups for use with woodwind instruments, such as oboes, clarinets, bassoons, saxophones and the like.

Magnetic pickups of the character of the present invention are used in conjunction with suitable audio frequency amplifiers and reproducing apparatus to provide an increased volume of sound.

It is an object of the invention to provide an electrical pickup which will convert the acoustic energy of a woodwind instrument into electrical currents and in which extraneous sounds such as clicks caused by manipulation of the keys will be minimized. Clicks, hissing sounds caused by passage of air through the instrument and noises produced by movements of the person playing the instrument will all be amplified along with the desired musical sounds when the usual microphone is utilized as a pickup. The invention confines the electrical currents produced to those resulting principall from the vibration of the reed of the instrument and to the substantial exclusion of the extraneous and undesired sounds incidental to the playing of the instrument.

It is a further object of the invention to provide a pickup of this type which is simple in construction, economica1 to manufacture and which will permit reproduction of the desired sounds with a high degree of fidelity.

It is another object of the invention to provide a pickup which will retain its adjustment notwithstanding jars, shocks and other mechanical disturbances which tend to cause displacement of the parts of the electromagnetic system.

Other and further objects will become apparent upon reading the following specification together with the accompanying drawing forming a part hereof.

Referring to the drawing:

Fig. 1 is a view in elevation of an embodiment of the invention.

Fig. 2 is an end view in elevation looking from the right of Fig. 1.

Fig. 3 is an enlarged sectional view taken along the line 3-3 of Fig. 2 looking in the direction of the arrows.

Fig. 4 is an enlarged sectional view taken along line 4-4 of Fig. 3, looking in the direction of the arrows thereof.

Fig. 5 isa perspective View of one of the armature stabilizing brackets. i

Fig. .6 is a-perspective view of one of the mag: netic pole pieces. l

Fig. 7 is a plan view of a bottom plate used in holding the housing together.

Referring now to Fig. 1, the usual mouthpiece II is provided with a reed l2 secured by a conventional reed clamp I3. A cork band I4 is shown provided at the end of the unit where it is fitted to the instrument.

A feeler member or vibrator I5 is in direct contact with the reed l2 and is fixedly but yieldingly supported in mouthpiece H by a sleeve iii of resilient material. A good grade of live rubber has been found to be suitable for this purpose and in other places in the invention where resilient material is required.

Secured to the upper end of vibrator I5 is an armature l6 and having upwardly spaced laterally extended arms forming a stabilizing member l7. Armature I6 is maintained in spaced relationship with respect to pole pieces I8 and the ends of stabilizing member H extend into and are maintained in spaced relationship with respect to apertures in stabilizing brackets in opposed U-shaped spring fingers which are lined at 29 with resilient material.

Pole pieces I8 are secured to magnet 2| by screws 22 which pass through holes 23 in the pole pieces. Electromagnetic coils 24 are disposed on pole pieces I 8 and are of conventional construction being electrically connected to a flexible cord 25 comprising conductors 26 and 21 which are adapted for connection to amplifying apparatus, not shown, in known manner. Magnet 2| may be permanently magnetized, a biasing current may be caused to flow in coils 24, or armature It may be permanently magnetized in order to provide a residual field. The residual field is desirable in order that the current variations generated in coils 24 will be directionally responsive to the movement of armature and further to cause the magnetic parts to operate in the steepest and most linear portions of their magnetization curves.

The shank of mouthpiece II is formed with a substantially square-shaped recess at 28 to fit magnet 2| which is secured thereto by cementing or other convenient :means to resilient material 29. Resilient material 29 absorbs mechanical vibrations incidental to manipulation of the woodwind instrument and prevents them from being transmitted to the magnet 2| and to the electroresponsive system comprising armature I6 and pole pieceslB. .Resilient material 29 isdisposed to prevent'any direct mechanical contact between mouthpiece Hand parts of the electromagnetic system.;

The electromagnetic system is enclosed by a cover spaced from magnet 2| by block of resilient material 42 and comprising two

symmetrical halves

30 and 3| secured together at their upper portions by screws 32 which are threaded into a link 33. At their lower portions the

cover halves

30 and 3| are held together by screws 33 which pass through holes 34 in a plate 35. Plate 35 is provided with a protruding portion 36 adapted to receive and engage a strain relief knot 31 in cord 25 at the point where cord 25 passes through plate.

Pole pieces l8 are provided with rectangular cutout portions 38 which are shaped to engage and guide shank portions 39 of armature stabilizing brackets l9. Brackets 19 are provided with elongated holes 40 permitting them to be adjustably secured to magnet 2| by screws 4|. The extending ends of armature stabilizing member H are shown in spaced relationship with respect to resilient material 29 carried by brackets I9 and screws 4! together with elongated holes 413 permit the position of the brackets IE to be varied so that this spacing may be maintained, as when a new reed i2 is inserted in mouthpiece H.

The pickup may also be arranged so that the resilient material 20 is in yielding engagement with the end portions of stabilizing member H. In this case the adjustment of brackets l3 will permit the adjustment of the air gap between armature l8 and pole pieces l8. This latter arrangement will reduce the magnitude of the armature travel but it will tend to increase the damping of the moving system comprising armature I6 and feeler l thus reducing the effects of possible mechanical resonance at critical frequencies in the moving system. Such resonance efiects will seriously impair the fidelity of reproduction.

Piezo-electric means, electrostatic means, a carbon ground device of any other suitable arrangement may be utilized in electro-responsive systems if desired instead of the electromagnetic means herein shown and described. Such an electro-responsive system would be arranged to respond to vibrations transmitted thereto by feeler member and would be insulated from mouthpiece II and cover 39-3l by resilient material to prevent the transmission of extraneous mechanical vibrations to the electro-responsive system.

In operation, vibrations of reed [2 are transmitted along feeler E5 to armature I6 which accordingly varies the magnetic reluctance of the air gap between the armature l6 and pole pieces i8. These variations in reluctance cause corresponding variations in the strength of the residual magnetic field with the accompanying generation of audio frequency voltages in windings 24 associated with pole pieces l8. Similar operation would be obtained with one of the alternative electroresponsive systems referred to above.

The audio frequency voltages thus generated are carried to suitable amplifying and reproducing apparatus as described. The voltages may be recorded or transmitted by wire or radio in the same manner as the output of a microphone.

I have shown what I believe to be the best embodiment of my invention. I do not wish, however, to be limited to the embodiment shown but by the invention as defined in the appended claims.

I claim:

1. In an electrical pick-up for wind instruments having a mouthpiece with a transverse peripheral recess intermediate the ends and having a reed and also a vibrator engaging the reed and extending diagonally through the mouthpiece, an armature comprising a plate with upwardly spaced laterally extended arms, a U-shaped magnet having arms connected by a thin base positioned in the recess of the mouthpiece, said magnet having a square inner area and the part of the mouthpiece positioned in the magnet being correspondingly shaped providing positioning means between the parts, a resilient liner between the mouthpiece and magnet, pole pieces having coils thereon removably mounted on the ends of the arms of the magnet, stabilizing brackets with opposed U- shaped fingers at the upper ends between which the ends of the laterally extended arms of the armature are positioned, and resilient material lining the inner surfaces of the said U-shaped fingers.

2. In an electrical pick-up for wind instruments having a mouthpiece with a transverse peripheral recess intermediate the ends and having a reed and also a vibrator engaging the reed and extending diagonally through the mouthpiece, an armature comprising a plate with upwardly spaced laterally extended arms, a U-shaped magnet having arms connected by a thin base positioned in the recess of the mouthpiece, said magnet having a square inner area and the part of the mouthpiece positioned in the magnet being correspondingly shaped providing positioning means between the parts, a resilient liner between the mouthpiece and magnet, pole pieces having coils thereon removably mounted on the ends of the arms of the magnet, stabilizing brackets with opposed U-shaped fingers at the upper ends between which the ends of the laterally extended arms of the armature are positioned, resilient material lining the inner surfaces of the said U-shaped fingers, and a suitable casing enclosing the said magnet and armature.

3. In an electrical pick-up for wind instruments having a mouthpiece with a transverse peripheral recess intermediate the ends and having a reed and also a vibrator engaging the reed and extending diagonally through the mouthpiece, an armature comprising a plate with upwardly spaced laterally extended arms, a U-shaped magnet having arms connected by a thin base positioned in the recess of the mouthpiece, said magnet having a square inner area and the part of the mouthpiece positioned in the magnet being correspondingly shaped providing positioning means between the parts, a resilient liner between the mouthpiece and magnet, pole pieces having coils thereon removably mounted on the ends of the arms of the magnet, stabilizing brackets with opposed U-shaped fingers at the upper ends between which the ends of the laterally extended arms of the armature are positioned, and resilient material lining the inner surfaces of the said U-shaped fingers, the lower thin surface of the magnet providing clearance whereby the reed extends over the magnet.

4. In an electrical pick-up for wind instruments having a mouthpiece with a transverse peripheral recess intermediate the ends and having a reed and also a vibrator engaging the reed and extending diagonally through the mouthpiece, an armature comprising a plate with upwardly spaced laterally extended arms, a U-shaped magnet having arms connected by a thin base positioned in the recess of the mouthpiece, said magnet having a square inner area and the part of the mouthpiece positioned in the magnet being correspondingly shaped providing positioning means between the parts, a resilient liner between the mouthpiece and magnet, pole pieces having coils 5 thereon removably mounted on the ends of the arms of the magnet, stabilizing brackets with opposed U-shaped fingers at the upper ends between which the ends of the laterally extended arms of the armature are positioned, resilient material 5 lining the inner surfaces of the said U-shaped fingers. a suitable casing enclosing the said magnet and armature, and resilient blocks spacing the casing from the mouthpiece, magnet, and armature.

ALFRED JOHNSON.

6 REFERENCES CITED The following references are of record in the I file of this patent:

UNITED STATES PATENTS Number