Hybrid sound radiation device for vibrating a heavy-weight rigid plate at audio frequencies
The hybrid sound radiation device according to the invention is used for vibrating a heavy-weight rigid plate at audio frequencies. The device comprises two voice coils arranged concentrically, the external voice coil being coupled to a fluid reservoir comprising a three-fluid medium having a substantially constant viscosity as a function of frequency. A third coil is arranged around the side wall of the fluid reservoir and two electrodes of opposite polarity are provided in the fluid reservoir for providing a substantially constant electric field inside the fluid reservoir. The device further comprises a vibrating element in the form of a heavy-weight, rigid, planar plate rigidly connected to the fluid reservoir; and control circuits connected to the first, second and third coils and the electrodes.
1 . A hybrid sound radiation device ( 100 ) for vibrating a heavy-weight rigid plate at audio frequencies, the device comprising:
a fixed support member ( 120 );
a permanent magnet ( 210 ), one end of which is fixed to the support member ( 120 );
a fixed first coil ( 220 ) arranged around the permanent magnet ( 210 ), the central axis of which defines a primary axial direction ( 110 );
a second coil ( 240 ) disposed around the first coil ( 220 ) and movable along the primary axial direction ( 110 ),
an intermediate member ( 140 ) to a first side of which an end of the second coil ( 240 ) remote from the support member ( 120 ) is attached and said intermediate member ( 140 ) is guided along guide support members ( 130 ) attached to the support member ( 120 ) and extends in the primary axial direction ( 110 );
a fluid reservoir attached to the second side of the intermediate member ( 140 ) opposite the first side, having a side wall of variable length along the first axial direction ( 110 ), and
wherein the fluid reservoir contains a medium ( 310 ) comprising at least one thixotropic fluid and a predetermined mixture of a rheopectic fluid and a magnetorheological fluid, wherein the three-fluid medium ( 310 ) has a substantially constant viscosity as a function of frequency, and
wherein a third coil ( 330 ) is arranged around the side wall ( 320 ) of the fluid reservoir, the central axis of which is parallel to the primary axial direction ( 110 ), and
wherein a first electrode ( 340 ) and a second electrode ( 350 ) of opposite polarity are provided in the fluid reservoir at its side connected to the intermediate member ( 140 ), the electrodes ( 340 , 350 ) providing a substantially constant electric field inside the fluid reservoir;
a vibrating element ( 160 ) in the form of a heavy-weight, rigid, planar plate rigidly connected to the side of the fluid reservoir opposite the intermediate member ( 140 ); and
control circuits ( 270 , 370 ) connected to the first, second and third coils ( 220 , 240 , 330 ) and the electrodes ( 340 , 350 ).
2 . The device of claim 1 , wherein the second coil ( 240 ) has a cylindrical annular support member ( 230 ).
3 . The device according to claim 1 , wherein the side of the support member ( 120 ) facing the intermediate member ( 140 ) and the side of the intermediate member ( 140 ) facing the support member ( 120 ) have a magnetic shielding element ( 250 , 260 ).
4 . The device according to claim 1 , wherein the material of the vibrating element ( 160 ) is gres, stone, glass or wood.
5 . The device according to claim 1 , wherein a vibration-transmitting element ( 150 ) is arranged between the fluid reservoir and the vibrating element ( 160 ).
6 . The device according to claim 1 , wherein the thixotropic fluid is a composite elastomer, in particular polydimethylsiloxane.
7 . The device according to claim 1 , wherein the rheopectic fluid is a mixture of lithium hydroxystearate and silicone oil.