1 . . . Limited

Cambridge Mechatronics Limited

David Henry Pearce

Anthony Hooley

Gareth McKevitt

Ursula Ruth Lenel

Mark Richard Shepherd

James Allan

Simon Andrew Longbottom

Luc Forest

Gareth Mckevitt

A loudspeaker comprising: a support, a sound-generating element mounted to the support for vibration to generate sound; and an electro-active device coupled between the support and the sound-generating element for vibrating the sound-generating element in response to an electrical signal. The electro-active device comprises a structure extending along a minor axis which extends in a curve around a major axis parallel to the vibration direction of the sound-generating element, the structure comprising successive electro-active portions arranged with electrodes to bend around the minor axis on activation in response to application of the electrical signal to the electrodes, and coupled together such that bending of successive portions causes concomitant rotation of adjacent portions around the minor axis adding incrementally along the minor axis, which rotation causes concomitant change of the axial length of the structure along the major axis.

Loudspeaker using an electro-active device

Various sensors use an electro-active device () electrically connected to a detector circuit. The electro-active device () comprises an electro-active structure in the form of a continuous electro-active member () curving in a helix around a minor axis () which is in itself curved for example in a helix around a major axis (). On activation by relative displacement of the ends () of the device (), the electro-active structure twists around the minor axis due to the fact that the minor axis () is curved. The continuous member () has a bender construction of a plurality of layers () and () including at least one layer of electro-active material so that concomitantly with the twisting the continuous member () bends generating an electrical signal detected by the detector circuit. The electro-active device () is advantageous as a sensing element in a sensor because it has a large displacement, high sensitivity and low compliance.

Sensor using electro active curved helix and double helix

A camera () uses an electro-active device () to position a movable lens. The electro-active device () comprises an electro-active structure in the form of a continuous electro-active member () curving in a helix around a minor axis () which is in itself curved for example in a helix around a major axis (). The continuous member () has a bender construction of a plurality of layers (and) including at least one layer of electro-active material so that it bends, on activation, around the minor axis (). Concomitantly with the bending, the electro-active structure twists around the minor axis. Concomitantly with that twisting, relative displacement of the ends () of the device () occurs due to the combination of the twisting around the minor axis () and the fact that the minor axis () is curved. This structure of the electro-active device () is compact and provides for linear displacement, thereby making it suitable for positioning the lens of the camera ().

Camera lens positioning using a electro-active device

The present invention relates to an electro-active device having an electro-active structure extending along a minor axis ( ) which is curved, for example in a helix around a major axis ( ). The electro-active structure comprises successive electro-active portions ( ) extending around said minor axis and arranged with electrodes to bend, when activated, around the minor axis ( ) such that bending of the successive portions ( ) is concomitant with rotation of the electro-active structure about the minor axis ( ) adding incrementally along the minor axis ( ). The electro-active structure generates displacement out of the local plane in which the minor axis is curved. The electra-active structure may be continuous electro-active member ( ) extending along and curving around the minor axis ( ), for example helically to form a helical helix. Alternatively, the electro-active structure may be a plurality of discrete elements ( ) connected together. The electro-active portions preferably have a bender structure formed from a plurality of layers. The device may be used as a driver, a sensor or a generator.

Electro active devices

In its first aspect the invention provides an electromechanical acoustic transducer ( ) which is resistively terminated at the rear with a closely-coupled sound absorber ( ) made from an aerogel with good acoustic absorption at low frequencies. The invention also provides an aerogel suitable for this use and which is a conglomerate of small particles packed so that there are spaces left therebetween to allow the passage of sound. Moreover, the invention provides an aerogel suitable for this use and comprised of multiple layers ( etc.) of materials of graded properties, or comprised of material of continuously varying properties throughout the thickness of the absorbing structure, in the principal direction of sound from the source.

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Birmingham, United Kingdom

David Henry Pearce