US3027541A

US3027541A - Structure for use in an electrodynamic transducer

Info

Publication number: US3027541A
Application number: US10587A
Authority: US
Inventors: Wilbur T Harris
Original assignee: Harris Transducer Corp
Current assignee: Harris Transducer Corp
Priority date: 1951-08-11
Filing date: 1960-02-24
Publication date: 1962-03-27
Anticipated expiration: 1979-03-27

Description

March 27, 1962 w. T. HARRIS 3, 7,

STRUCTURE FOR USE IN AN ELECTRODYNAMIC TRANSDUCER Filed Feb. 24, 1960 //3 w //z Z IN VEN TOR. W/ 8M? 77 697 6 45 ayg/umkM/m 3,027,541 Patented Mar. 27, 1962 3,027,541 STRUCTURE FOR USE IN AN ELECTRO- DYNAMIC TRANSDUCER Wiibur T. Harris, Woodbury, Conn., assignor to The Harris Transducer Corporation, Woodbury, Cornn, a

corporation of Connecticut Filed Feb. 24, 1960, Ser. No. 10,587 4 Claims. (Cl. 340-42) My invention relates to structures for use in electroacoustic transducers suited to underwater operation.

This application is a continuation in part of my prior application Serial No. 241,470 of August 11, 1951, en-

titled, Electrodynamic Transducer, now Patent No. 2,978,671 of April 4, 1961.

In the said prior application Serial No. 241,470 (now Patent No. 2,978,671) a number of transducer constructions are disclosed in which the vibration-producing elements are supported on bodies of sound-attenuating material or the like, and in which certain improved structures are disclosed for providing a magnetic circuit within which those vibration-producing elements are supported. The present invention relates to a magnetic stmcture per se, suitable for use in an electroacoustic transducer of the type under discussion, and is specifically disclosed in an embodiment in which the vibration-producing elements are not mounted on sound-attenuating bodies. The arrangement of the parts of the structure of the present in vention produces a structure which is electromagnetically Effective, reliable, and readily manufactured and assem- 1 ed.

It is, accordingly, an object of the invention to provide an improved structure for use in a transducer of the character indicated.

It is another object to provide a transducer having high efficiency over an extended frequency range.

It is a further object to provide an improved non-resonant transducer.

Another object is to provide an improved, relatively highly efiicient transducer for electroacoustic or acoustoelectric conversion in water and having further useful application in air.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings, in which the figure is a fragmentary cross-sectional view of a preferred embodiment of the present invention.

As has been stated above, the embodiment in the figure discloses a transducer in which the active vibration-producing strips 1% are not supported on bodies of sound attenuating material or the like, but which embodies an effective and efficient and magnetic circuit arrangement. The active strips 100, laminated to reduce eddy current losses, are interposed between the bar magnets 192 which are polarized and arranged as shown. The magnets 102 are secured in any appropriate manner to supporting struts 1% of non-magnetic material which extend between the magnets 102 and a bottom plate 106 of magnetic material. The struts 104 are provided with central openings 198 in order that the spaces between the struts 104 may communicate with one another. The magnetic bottom plate 186 is provided with an upstanding end wall 110, preferably integral therewith, which is also formed of magnetic material and with which the end magnet 102 is in operative magnetic connection, as by abutting directly thereagainst. The bottom wall 106 may be provided with a plurality of openings 112 therethrough communicating between the lower edge of the bottom plate 106 and the spaces between the struts 104. The entire assembly is surrounded by an acoustically transparent rubber sheath 114, the conductive strips being mounted directly on the underside of the upper portion of that rubber sheath 114 in any appropriate manner so as to be operatively interposed between the opposite magnetic poles of a pair of magnets 102. The interior space of the transducer of the figure is adapted to be filled with a liquid, which may have an acoustic impedance equal or close to that of water, although water itself is not preferred for reasons which are not acoustic in nature, such as lack of insulative properties and tendency toward corrosion. Accordingly the filling liquid is preferably a low viscosity liquid having good electrical insulating properties, such as a low molecular weight" silicone fiuid. The active strips 1% are, of course, formed of electrically conductive material, such as copper. They may be electrically connected in parallel to a suitable source of electrically, but since this would make for unduly low electrical impedance, I prefer that they be series connected. The openings 112 in the bottom wall 106 permit acoustic radiation through that bottom wall, and also provide for pressure compensation, so that the active strips 100 will remain properly positioned within the air gaps between the magnets 102 substantially independent of the depth beneath the surface of the sea at which the transducer is operating. The magnetic circuit extends straight across the top of the device from one magnet 102 to the other, and therefore directly across the gaps in which the active strips 11%) are located, the return magnetic path being defined by the substantially continuous end wall 110 and bottom wall 1&6, which are formed of magnetic material as aforesaid.

It will be seen that I have described novel acoustoelectric and electro-acoustic transducer means applicable to air and water use. The construction provides especially advantageous underwater features, including great power-handling capacity over a relatively broad frequency band. The basic construction is relatively simple and lends itself to arrays of almost any desired configuration.

While I have described my invention in detail for the preferred forms shown, it will be understood that modifications may be made within the scope of the invention, as defined in the following claims.

I claim:

1. In a transducer of the character indicated, a series magnetic circuit comprising a series of spaced bipolar permanently magnetized elements defining a series of polarized gaps, ferromagnetic means independent of said permanently magnetized elements interconnecting the outer ends of the outer of said elements, whereby the series magnetic circuit may be closed, and electrically conducting means movably supported in the gaps be tween said elements, in which said ferromagnetic means comprises a part extending beneath and spaced from said magnetized elements, and non-magnetic means interposed between and engaging said part of said ferromagnetic means and said magnetized elements and constituting supports for the latter on the former.

2. The transducer of claim 1, in which said non-magnetic means only partially fills the space between said magnetized elements and said ferromagnetic means, and a liquid filling the remainder of said space.

3. In a transducer of the character indicated, a housing comprising side and bottom walls of ferromagnetic material, a series magnetic circuit comprising a series of spaced bipolar permanently magnetized elements across the top of said housing defining a series of polarized gaps, the outermost of said permanently magnetized elements being magnetically operatively connected to the side walls of said housing, said side and bottom walls of said housing defining a ferromagnetic means independent of said per- References (Zited in the file of this patent UNITED STATES PATENTS Evershed et :11. Mar. 9, 1920 Riegger Oct. 26, 1926 Vasilach Aug. 18, 1942 Olson Oct. 14, 1947 Merten Dec. 6, 1949 Bardeen et a1 Sept. 6, 1955