US2235983A

US2235983A - Magnetic pickup construction for electrical musical instruments

Info

Publication number: US2235983A
Application number: US232526A
Authority: US
Inventors: Galan W Demuth
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1938-09-30
Filing date: 1938-09-30
Publication date: 1941-03-25
Anticipated expiration: 1958-03-25

Description

March 2 5, 1941.

MAGNETIC PICKUP CONSTRUCTION FOR ELECTRICAL MUSICAL INSTRUMENTS Filed Sept. 30, 1938 v z 1 [L lli/[IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII/IIII1M Zhwentor G. w. DEMUTH 2,235,983

Patented Mans, 1941 PATENT "OFFICE MAGNETIC PICKUP CONSTRUCTION FOR Enscrnrcsr. MUSICAL msraumnn'rs Galan W. Demuth, Westviiie, N. 1., assignor to Radio Corporation of America, a corporation Delaware 1 Application September 30, 1938, Serial No. 232,526

6 Claims.

This invention relates to magnetic'pickup construction for use in electric musical instruments and more particularly adapted for use in electric pianos and other types of stringed musical in- D struments having a plurality of magnetic strings.

Pianos and analogous instruments are'provided with a series of strings having diameters depending on the notes of the scale to be produced and these strings particularly in pianos vary not only 10 in size but in numbers according to the notes. It

has heretofore been customary to make special pickups for each note of the scale of appropriate dimensions to most effectively pick up each note. Such an arrangement, however, is extremely unis satisfactory commercially since the pickups are made to predetermined size and shape and if they do not happen to be exactly suited to the particular note which is to be reproduced it is necessary to make a new pickup to accommodate that par- 20 ticular note. Such an arrangement is extremely unsatisfactory in the commercial production of electric musical instruments since it leaves a large portion of the pickups to be hand-fitted and ad- Justed in each instrument. In pickups made ac- 25 cording to my invention all the pickups may be made alike and may be readily adjusted according to which note they are intended to accommodate. I accomplish this result by making the pickups in the form of flat coils wound on a list 30 sott core and by similarly making the exciting magnets in the form of flat bars. Both the magnets and the soft core have a thickness commensurate with the width of'a single string and have a breadth corresponding with the outside 35 dimension of the broadest group of strings for a single note in the type of instrument for which the pickup is to be used.

One object of the invention is to provide an improved pickup having a high electric efficiency. 40 Another object of the invention is to provide an improved type of pickup adapted to single strings or to groups of strings.

Another object of the invention is to provide an improved type vof pickup which may be readily manufactured in considerable quantities.

Another object of my invention is to provide a pick-up which is adapted to efficiently pickup impulses from strings which are crowded close together.

50 Another object of my invention is to provide a pickup which is of suillcient size to be adapted to uniformly pick up the impulses from large groups of strings.

Other and incidental objects of the invention 55 will be apparent to those skilled in the art from a reading of the following specification and an inspection of the accompanying drawing, in which- Fgure 1 is a side view of my improved pickup in proper relation to a string; 5

Figure 2 is a view from the bottom of Figure 1 showin the relation of a single bass string to the pickup and the magnet;

Figure 3 is a view corresponding to Figure 2 by showing the relation of the pickup coil and magnet to a group of treble strings arranged as a triple unison; and

Figure 4 is a view corresponding to Figures 2 and 3 showing a pickup coil and magnet as arranged in relation to a group of two strings in a double unison as occurring in the middle range of the piano.

Referring first to Figure 1, a bass piano string is indicated at I, 2, I being the-core and I being the winding thereon. A permanent magnet prefg erably of the material known as nlpermag for producing the necessary magnetic field is shown at I, which is attached to a soft metal plate I by means'of solder is indicated at I. A soft metal core I is likewise attached to the plate 8 by means of a threaded extension II and the nut II. The plate 8' and core I are preferably made of cold rolled steel or soft iron. Over this soft metal core there is provided a winding t having the leads I. The magnet l and the core I are made in approximately the shape shown and of a thickness as shown in Figure 2 of the same order as 'the width of one of the bass strings of the piano. The magnet is not necessarily, but is preferably flat, as shown, but it may be of any other convenient shape. It is impractical to fasten the magnet 3 to the plate 8 in the same manner as the core I is fastened, due to the extreme hardness of the permanent. magnets used.

It will be apparent that in this arrangement 40 the largest possible area of the faces of the magnet I and of the core 5 are presented to the piano string i, 2.

When it is desired to use the magnetic pickup for a triple unison in the higher notes of the piano, the arrangement in Figure 3 is used where the magnet 3 and the core 5 are turned so as to be transverse of the strings. In this case, due to the width of their faces the magnet equally affects all three strings while the pickup is equally affected by all three strings.

In the application of the invention shown in Fig. 4, the pickup is applied to a double unison in the middle range of the piano. In this case, both the magnet 3 and the soft core 5 with the pickup coil 6 are turned at such an angle as to adequately cover the two strings B3. The members 3 and 5 could, of course, be turned directly across the strings l3, as shown in Fig. 3, but this would require more space and would not permit the pickups to be placed as closely together as the pairs of strings for the several notes are usually placed, while the turning of the members 3 and 5 at an angle as shown, leaving them project only far enough beyond the strings to provide sufllcient pickup, minimizes the space required without any decrease in efilciency.

The soft metal plates 8 of the pickups corresponding to the several notes of an instrument are, of course, mounted on an appropriate support such, for example, as a long supporting strip which may reach completely across an entire group of strings.

It is apparent from the foregoing description that my improved pickup can be applied to single strings or groups of strings and that the only modification necessary is the turning of the soft core and of the polarizing magnet to the proper angle to the axis of the string or string assembly.

Having now described my invention, I claim:

1. In a magnetic pickup for cooperation with one or more strings, the combination of a magnetizable plate of soft material, a pair of pole pieces secured endwise thereto, said pole pieces including a permanent magnet thin in relation to its width and a second pole piece of magnetizable material also thin in relation to its width, a pickup coil surrounding at least one of said pole pieces, both of said pole pieces being adapted to be placed at various angles to the axis of said plate according to the number of the vibrating elements they are intended to cooperate with.

2. In a magnetic pickup for cooperation with one or more strings, the combination of a magnetizable plate of soft material, a pair of pole pieces secured endwise thereto, one of said pole pieces being a permanent magnet thin in relation to its width, the other pole piece being of magnetizable material and thin in relation to its width, a pickup coil surrounding at least one of said pole pieces, both of said pole pieces being in parallel planes at'such angles to the axis of said strings as to most efiectively cooperate with either a single string or a group of strings, according to which the pickup is intended to cooperate with.

3. A magnetic pickup of the type described including a magnetizable plate of soft material, a

permanent magnet thin in relation to its width secured perpendicularly thereto. a core of soft magnetizable material thin in relation to its width and likewise secured perpendicularly to said plate, and a pickup coil surrounding said soft core, both said magnet and said core being adapted to be placed at various angles to the axis of said plate according to the member of the vibrating elements they are intended to cooperate with.

4. a magnetic pickup of the type adapted to cooperate with one or more strings including a magnetizable plate of soft material, a permanent magnet thin in relation to its width secured perpendicularly thereto, a core of soft magnetizable material thin in relation to its width and likewise secured perpendicularly to said plate, and a pickup coil surrounding said soft core, both said magnet and said core being in parallel planes at such angles to the axis of said strings as to most eflectively cooperate with either a single string or a group of strings, according to which the pickup'is intended to cooperate with.

5. In combination with a musical instrument having varying numbers of strings corresponding to different notes, a magnetic pickup for each note, each said pickup having pole pieces including a permanent magnet thin in relation to its width, a core of soft magnetizable material thin in relation to its width and surrounded by a pickup coil, each pickup permanent magnet and core being secured to a magnetizable plate of soft material in such relation to the strings of the note with which the pickup is intended to cooperate that the dimension of the pickup pole pieces measured transversely of the strings will correspond with the transverse distance across said strings.

6. In combination with a musical instrument having varying numbers of strings corresponding to different notes, a magnetic pickup for each note, each said pickup having pole pieces including a permanent magnet thin in relation to its width, a core of soft magnetizable material thin in relation to its width and surrounded by a pickup coil, each pickup permanent magnet and core being secured to a magnetizable plate of soft material in such relation to the strings oi the note with which the pickup is intended to cooperate that the dimensions of the pickup pole pieces measured transversely of the strings will correspond with the transverse distance across said strings, all of said pickups having similar magnets and similar cores.

GALAN W. DEMUTH.