US2890289A

US2890289A - Ribbon-type magnetic armature transducer

Info

Publication number: US2890289A
Application number: US742452A
Authority: US
Inventors: Ross M Carrell
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-06-16
Filing date: 1958-06-16
Publication date: 1959-06-09
Anticipated expiration: 1976-06-09

Description

June 9, 1959 R. M. CARRELL 2,890,239

RIBBON-TYPE MAGNETIC ARMATURE TRANSDUCER Filed June 1a, 1958 INVENTOR. E M CHEEELL IBM/w.

WMZZZZ United States Patent RIBBON-TYPE MAGNETIC ARMATURE TRANSDUCER Ross M. Carr-ell, Westmont, N.J., assiguor to the United States of America as represented by the Secretary or the Air Force This invention relates to a ribbon-type magnetic armature transducer which has a lower mechanical impedance than prior art devices and which, therefore, gives an increased efliciency.

One object of the invention is to provide a magnetic armature transducer which has less movable mass than prior art devices and which, therefore, has a better impedance match with the air.

This and other objects will be more fully understood from the following detailed description taken with the drawing wherein:

Fig. 1 is a top view of a magnetic armature transducer according to a preferred embodiment of the invention.

Fig. 2 is a sectional view of the device of Fig. 1 taken along the lines 2-2.

In ordinary magnetic armature transducers, the ribbon armature must be made stiff to offset the attraction of the pole pieces. Making the armature stilt implies thickness which means added mass. According to this invention, the stiffness is obtained by placing the armature under tension thereby permitting the use of much thinner material. Armature thicknesses of .001 inch are possible, however, this would require very accurately balanced magnetic fields so that no D.C. flux flows through the armature to produce saturation and perfect balance is very difiicult to achieve in practice. Therefore, an armature thickness slightly greater than .001 inch is required. In order to keep the total moving mass low, the armature is coupled to the diaphragm by a thin wire which is kept under tension by a spring. The compliance of the spring should be large compared with that of the diaphragm. The pole pieces are constructed so that their reluctance is about percent of that of the air gap. Magnetic shunts are then provided to modify the reluctance of the pole pieces to adjust the fields so that the magnetic center of the structure coincides with the armature.

Referring now to Fig. 1 of the drawings, reference character 10 refers to a magnetic armature transducer having a thin armature ribbon 11. As shown in Fig. 2, armature ribbon 11 is supported on support posts 12 and 13. The thickness of the armature should be approximately .001 inch.

Magnetic pole pieces

14 and 17 are located on one side of the armature and pole pieces 21) and 23 are located on the opposite side thereof. Pole piece 14 has projections 15 and 16 extending toward the armature. Pole piece 17 has

projections

18 and 19 extending toward the armature. Pole piece 20 has projections 21 and 22 extending toward the armature and pole piece 23 has projections 24 and 25 extending toward the armature. A permanent magnet 26 is located between the

pole pieces

14 and 20 and a permanent magnet 27 is located between the

pole pieces

17 and 23. The output is taken off by means of coils 30 and 31 which encircle the armature 11 and which are located between 7 the

pole pieces

14 and 20 and 17 and 23, respectively.

The coils 30 and 31 are connected in series aiding. A

diaphragm 32 is supported within a housing 33 in the usual manner and is coupled to the armature 11 by means of a thin wire 34. The wire 34 is kept under tension by means of a spring 35 which is attached to the armature 11 by means of a thin wire 36. The compliance of the spring 25 should be made large compared with that of diaphragm 32.

Magnetic shunts

37 and 38 are provided adjacent the

pole pieces

14 and 17 to adjust the reluctance of these pole pieces so as to make the magnetic center of the structure coincide with the armature so that no D.C. flux will flow through the armature. As can be seen from Fig. 1, the

magnetic shunts

37 and 38 are located adjacent two

holes

39 and 40 in the pole pieces. Though the hole is shown as being rectangular in shape in this figure, it is obvious that other configurations, as well as other locations for the shunt elements, could be used.

There is thus provided a ribbon-type magnetic armature transducer which has less moving mass than prior art devices and which, therefore, provides an increased efiiciency.

While one specific embodiment has been described in some detail, it is obvious that numerous changes may be made without departing from the general principles and scope of the invention.

What is claimed is:

1. A magnetic armature transducer, comprising; a thin ribbon-type armature, means for supporting said armature under tension, a first pole piece located on one side of said armature, a second pole piece located on the other side of said armature, means for producing a magnetic flux in said pole pieces, means adjacent said first pole piece for adjusting the magnetic circuit through said pole pieces to thereby make the magnetic center of the structure coincide with said armature, a diaphragm, means for coupling said diaphragm to said armature and a coil located in energy-coupling relation with said armature.

2. A magnetic armature transducer, comprising; a thin ribbon-type armature, means for supporting said armature under tension, a first pole piece located on one side of said armature, a second pole piece located on the other side of said armature, means for producing a magnetic flux in said pole pieces, means adjacent the pole piece on one side of said armature for adjusting the magnetic circuit through said pole pieces to thereby make the magnetic center of the structure coincide with said armature, a diaphragm, a thin wire for coupling said diaphragm to said armature, means connected to the other side of said armature for holding said wire under tension and an output coil located in energycoupling relation with said armature.

3. A magnetic armature transducer, comprising; a thin ribbon-type armature, means for supporting said armature under tension, a first set of pole pieces located on one side of said armature, a second set of pole pieces located on the other side of said armature, means for producing a magnetic flux in said pole pieces, means adjacent the pole pieces on one side of said armature for adjusting the magnetic circuit through said pole pieces to thereby make the magnetic center of the structure coincide with said armature, a diaphragm, a thin wire for coupling said diaphragm to said armature, means connected to the other side of said armature for holding said wire under tension, and output coils located in energy-coupling relation with said armature.

4. A magnetic armature transducer, comprising; a thin ribbon-type annature, means for supporting said arma- O ture under tension, a first set of pole pieces located on producing a magnetic flux in said pole pieces, a magnetic shunt adjacent the pole pieces on one side of saidarmature for adjusting the magnetic circuit through said pole pieces to thereby make the magnetic center of the structure coincide with said armature, a diaphragm, means having a low mass for coupling said diaphragm to said armature, means connected to the other side of said arrnature for holding said coupling means under tension, and a pair of output coils located in energy-coupling relation with said armature.

5. A magnetic armature transducer, comprising; a thin ribbon-type armature having a thickness approximately .001 inch, means for supporting said armature under tension, a first set of pole pieces located on one side of said armature, a second set of pole pieces located on the other side of said armature, means for producing a magnetic flux in said pole pieces, a magnetic shunt adjacent said first set of pole pieces for adjusting the magnetic circuit through said pole pieces to thereby make the magnetic center of the structure coincide with said armature, a diaphragm, a thin Wire for coupling said diaphragm to said armature, means connected to the other side of said armature for holding said wire under tension and a pair of output coils located in energy-coupling relation with said armature.

No references cited.