1 . . . Limited

Gareth McKevitt

Mark Richard Shepherd

Anthony Hooley

David Henry Pearce

Ursula Ruth Lenel

Richard John Topliss

James Allan

Andrew Matheson

Simon Andrew Longbottom

David Livingstone

Matthew John Pitts

A piezoelectric device comprising a continuous piezoelectric element () extending alternately back and forth to form a plurality of parallel, straight portions () arranged in a stack with intermediate linkage portions () at alternate ends of the straight portions (). Each straight portion () is constructed and arranged with electrodes () to bend, on activation, in the stacking direction in which the straight portions () are stacked with opposite curvature in two halves () of the straight portion () to create displacement between the ends of the straight portion () in the stacking direction adding in series through the stack. The continuous nature of the piezoelectric element () eases manufacture. Devices with two types of construction are disclosed. Firstly, the continuous piezoelectric element () may have a bender construction such as a bimorph bender construction. Secondly, the continuous piezoelectric element () may be a sheet of piezoelectric material having overlapping slits () extending from alternate sides to form the straight portions () between the slits (), with opposed electrodes () arranged on each major surface of the sheet in pairs separated across, and extending along, the straight portions ().

Piezolelectric devices

A loudspeaker for audible sound is described having a sound emitting element mounted onto a support structure and at least one actuator adapted to rotate said sound emitting element around a hinge section, wherein the actuator is made of piezoelectric material. In variants the actuator forms part of the hinge section and the loudspeaker is capable of generating vibrations through its support structure.

Loudspeaker

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

An equivalent to the spatial separation either side of a nominal median plane that is inherent in a bimorph (with one piezoelectric layer on one side, and the second on the other side of the plane) is attained by structurally shaping the cross-section of a simple, single piezoelectric layer () such that it has a multiplicity of piezoelectric portions arranged in two generally-planar groups one either side of a median plane, so that any dimension change undergone by a portion on one side of that plane will tend to bend the whole device in the opposite direction to the same sense dimension change undergone by a portion on the other side of that plane. The simple, single layer acts as though it were a bimorph if elongate and beam-like, bending along its length, one end moving up/down, or back/forth, relative to the other but with any need for an internal, electrode.

Piezoelectric structures

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.

Growing community of inventors

Cambridge, United Kingdom

Gareth McKevitt