Vibration exciter

Details Vibration exciter Vibration exciter

2000-03-03

2001-12-25

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S051000

Reexamination Certificate

active

06333575

ABSTRACT:

TECHNICAL FIELD
The invention relates to a vibration exciter and more particularly, but not exclusively, to an inertial electrodynamic vibration exciter for exciting bending waves in a resonant panel to provide an acoustic output. Such devices are the subject of our co-pending International patent application WO97/09859.
BACKGROUND ART
One previous design for a balanced vibration exciter suitable for embedding within an acoustic panel radiator uses a pair of disc magnets coupled with poles opposing via a plate of magnetically permeable material such as mild steel. The result is a strong radial field enveloped around the plate which acts on a coil coupled to the radiating element. Of balanced design this exciter may be embedded symmetrically within the panel radiator and the coupling may be arranged so that both sides of the panel are equally coupled.
Alternatively, it is known to employ a cup type of exciter placed on one side or skin of the acoustic panel and this relies on good mechanical coupling through the panel to ensure equal or near equal acoustic output from both sides of the panel.
Two difficulties arise with the radial field type of exciter in specific applications. If high acoustic power is required the electrical input must be raised. This brings consideration of the thermal power in the exciter coil and the means for safely dissipating the excess heat.
Some gain in thermal dissipation can be achieved by using a thermally conductive carrier for the coil, coupled to global, or locally thermally conductive skins. Thus the heat within the panel is conducted outside and is radiated away.
DISCLOSURE OF INVENTION
According to the invention there is provided a vibration transducer adapted for location at least partially in a cavity in a member to be vibrated, comprising a motor coil assembly having a coil rigidly fixed to a tubular member, the motor coil assembly having an outer peripheral face, a magnet assembly disposed concentrically of the motor coil assembly and arranged for axial movement relative thereto, the magnet assembly having opposed generally disc-like pole pieces, the periphery of one of which is disposed within and adjacent to the motor coil assembly, and the periphery of the other of which pole pieces is formed with a flange arranged to lie adjacent to and to surround the motor coil assembly, the flange having aperture portions through which the outer peripheral face of motor coil assembly can be fixed directly to the member to be vibrated. The aperture portions thus form “windows” in the flange of the said other pole piece through which the motor coil assembly can be fixed to the member to be vibrated. The aperture portions may be created by forming the flange with cut-away portions or slots. The exciter may be an inertial device. The member to be vibrated may be panel-form.
Resilient means may be provided for supporting the magnet assembly for axial movement relative to the motor coil assembly. The resilient suspension may be adapted for fixing to the member to be vibrated. The resilient suspension may be mounted on the said other pole piece.
From another aspect the invention is a loudspeaker comprising a vibration transducer as described above.
From yet another aspect the invention is an assembly comprising a vibration exciter as described above and a resilient panel member in which the exciter is mounted.
There may be any number of aperture portions, i.e. two or more, to provide versatile options for coupling of the coil to the panel, for example to optimise the matching of the relative mechanical impedances for control of the frequency response of the assembly. The inertial mass represented by the magnet assembly is compliantly fixed to the panel or an intermediate carrier or frame such that good centering is maintained between the coil and the defined magnetic gap. Many suspension constructions are possible including an annular corrugated suspension, or small foam rubber pads.


REFERENCES:
patent: 4680492 (1987-07-01), Tamura
patent: 5602432 (1997-02-01), Mizutani
patent: 0 517 497 (1992-12-01), None
patent: 0 722 260 (1996-07-01), None
patent: WO 97/09859 (1997-03-01), None

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