US 2557754 A
Description (OCR text may contain errors)
June 19, 1951 Gf; MORRlsON 2,557,754
MAGNETIC PICKUP UNIT FR GUITARS y Filed July 12, 1949 a INVENToR. i @ur/zie EMorrz'So/z/ HIS' A TT'ORNEY 3 player of the instrument for changing the volume of sound emanating from the pick-up unit.
The magnetic pick-up unit 3i? of the present invention, as best seen in Figs. 2 through 6, comprises a center core of non-conductive material having a plurality of bores i formed therein corresponding in number to the number of strings di and spaced to coincide therewith. rThis core 55 is cemented at top and bottom to a tcp plate 52 and a bottom plate 53, respectively, each of which is provided with a plurality of holes, each aligning with and in registration with the respective bores 5i in the core. A Very fine wire is wound around the core 55 about ve thousand turns to comprise a coil 3l and the respective ends of this wire are the leads, mentioned above as being connected to the potentiometers 45 and 46.
The coil 3l is closed in by cementing a front plate 5 and side plates 55 and 56 to each other and to the top and bottom 52-53 and thereafter the balance of the space surrounding the core and coil is lled with paraffin. The back of the parafn lled coil portion is then closed by cementing the bridge block 32 to the top, bottom and side plates 52, 53, 55 and 55 so that the coil portion 5| and bridge block 32 become integral with each other.
Disposed in each bore 5l and adapted to extend through the holes registering with the bore is a permanent bar magnet 6G. These bar magnets are of a length adapted to extend into respectively aligned holes 5l formed in the spine or neck il of the instrument. Each bar magnet 60 is held in place by a set-screw 52 threadedly associated with a tapped bore 53 extending from the bar magnet to the forward edge of the bottom plate 55. In this manner when the unit 30 is removed from the pocket 25 in the panel lli, the set-screws 52 can be manipulated and the bar magnets shifted within their respective bores 5l to dispose the upper ends of the magnets above or below the upper surface of top plate 52, i. e. close to or substantially spaced from the particular wire string 4i associated therewith.
Referring now to Fig. '7 wherein the eddy currents or iields of adjacent magnets are shown in phantom, it will be noted that the field of each magnet is confined to the particular space allotted it. That is to say, since the polarity of each bar magnet is the same, the magnetic forces thereof repel each other and are confined to space allotted each bar magnet. Moreover, it will be noted that the string 5I above each magnet lies within the iield of its respective magnet 6D and since the strings di are ,of metal the eld in which each string lies is correspondingly distorted due to the magnetic attraction of the field toward such string.
From the foregoing it will be understood that any motion of a string from side to side of the vertical center of its related bar magnet attracts the magnetic field thereof from side to side, setting up a disturbance in the winding of the induction coil 3l. In this connection it will be noted that only the iield of the bar magnet related with a particular vibrating string is aected thereby and consequently the true tonal value of such string will not become discordant by reason of entrance of such string into the magnetic field of an adjacent bar magnet. Hence a clear tone is at all times assured.
It will be apparent to those skilled in the art that the device described herein is but one speoic form and structural aspect of the inventionwhich is susceptible to variations and modifications without departure from the spirit of the invention. I therefore desire to avail myself of all modifications, variations and alterations in structure coming within the purview of the appended claims.
What I claim as new and desire to protect by Letters Patent is:
l. In a pick-up unit for an electrically amplimetal stringed musical instrument comprising a core, an induction coil around said core, a tcp and bottom plate secured to said core, end Walls secured to said top and bottom plates, a bridge block secured to the edges of said top and bottom plates and said end walls at one side thereof, a side wall secured to the edges of said ton and bottom plates and the edges of said end we s that side of the core opposite said bridge block, said core having a plurality of bores spaced from each other so as to register with the strings of said instrument and to be dispcs-ed with the axes of said bores perpendicular to se d strings, a permanent bar magnet disposed in each cf said bores with common poles of said bar magnets disposed in substantially the same pi. Ae as each other so that the magnetic forces magnets repel each other to confine the magnetic iield of each bar magnet to the laterally extending Zone of each string of said instrument, and set-screws threadedly associated with said bottom plate and in alignment with each of said bar magnets fcr securing the latter position vertically relative to said core and the strings of said instrument.
2. In a pick-up unit for an electrically amplied metal stringed musical instrument comprising a core, an induction coil around said core, a top and bottom plate secured to said core, end walls secured to said top and bottom plates, a bridge block secured to the edges of said tcp and bottom plates and said end walls at one side thereof, a side wall secured to the edges of said top and bottom plates and the edges of said end walls on that side of the core opposite said bridge block, said core having a plurality of bores spaced from each other so as to register with the strings of said instrument and to be disposed with the axes of said bores perpendicular to said strings, and a permanent bar magnet secured in each of said bores with common poles of said bar mag-- nets disposed in substantially the same plane as each other so that the magnetic forces of adjacent magnets repel each other to conne the magnetic field of each bar magnet to the laterally extending zone of each string of said instrument.
GURNIE E. MORRISON.
REFERENCES CITED The following references are of record in the iile of this patent:
Sunshine Oct. l0, 1939