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Christopher A. Goat, Kent GB

Patent application numberDescriptionPublished
20100025065 CASING FOR AN ELECTRICAL COMPONENT - A casing for encapsulation of an electrical component, for example a piezoelectric actuator, comprising an outer layer of a semipermeable material and an inner layer comprising a chemically active, hydrophilic substance that chemically combines with water to form a compound.02-04-2010

Christopher Andrew Goat, Kent GB

Patent application numberDescriptionPublished
20090026890Reducing stress gradients within piezoelectric actuators - Piezoelectric actuators of the type comprising a stack of layers of ferroelectric material and intervening electrodes which extend only part-way across the adjacent ferroelectric layers suffer differential remanent stress when electric fields are applied across the layers. To overcome this, a tensile stress is applied to the actuator along an axis substantially perpendicular to the layers of piezoelectric material in the actuator, which tensile stress is sufficient to mechanically align the dipoles, thus giving rise to a remanent strain which is uniform throughout the actuator. The actuator is advantageously heated while the tensile stress is applied, so as to increase the difference between the tensile strength of the material and the applied tensile stress. An alternative arrangement involves subjecting the actuator to a multidirectional stress and reducing the stress along the axis substantially perpendicular to the layers of piezoelectric material in the actuator. The entire process is performed on completed actuators. Under suitable temperature and load conditions no tensile margin fractures form and electrode tip discontinuity is reduced.01-29-2009
20090152991Ferroelectric Durability - A piezoelectric actuator for use in a fuel injection system of an internal combustion engine, the actuator comprising a stack of ferroelectric layers; an encapsulation for protecting the stack from the ingress of liquid; and oxygenation means for providing oxygen to the ferroelectric layers, the means positioned between the encapsulation and stack. The oxygenation means is preferably impregnated in a fabric which forms a layer between the encapsulation and the stack.06-18-2009
20100237751PIEZOELECTRIC ACTUATOR - A piezoelectric actuator comprises a co-fired stack of piezoelectric elements formed from a piezoelectric material and a plurality of positive internal electrodes interdigitated with a plurality of negative internal electrodes throughout the stack to define active regions of the piezoelectric material which are responsive to a voltage applied across the internal electrodes, in use. An external positive electrode connects with the positive internal electrodes and an external negative electrode connects with the negative internal electrodes. The actuator is characterised in that the stack further comprises means for deliberately creating artificial cracks within the stack at a location at which the artificial cracks do not give rise to a short circuit between the internal electrodes but serve to relieve stresses within the piezoelectric material.09-23-2010

Christopher Andrew Goat, Offham GB

Patent application numberDescriptionPublished
20090038130Method for manufacturing a piezoelectric actuator - A method for manufacturing a piezoelectric actuator, the method comprising: co-extruding alternating strips of a high permittivity material and a low permittivity material to form a green tape comprising said alternating strips of said high permittivity material and said low permittivity material; cutting said green tape to form a plurality of sheets, each sheet comprising a high permittivity region and at least two low permittivity regions adjacent to the high permittivity region; applying at least one conductive region to each one of two or more of the sheets to overly the high permittivity region and to leave exposed at least one low permittivity region; and stacking a plurality of sheets to form an actuator stack comprising adjacent sheets, wherein the or each conductive region on each sheet is offset with respect to a conductive region on a different sheet within the actuator stack.02-12-2009

Christpher Andrew Goat, Kent GB

Patent application numberDescriptionPublished
20090302135Protective Encapsulation - An electrical device such as a piezoelectric actuator is protected against permeation by injurious fluids such as fuel (diesel/gasoline) and water by encapsulating the device with a shape memory metallic material. The shape memory metallic material may be in the form of a tube manufactured to the required dimensions for encapsulation of the device. The tube may then be plastically deformed, such as by stretching, before being placed over the device and heated above its transformation temperature to recover its original shape. The invention is particularly suitable for protecting passivated piezoelectric actuators.12-10-2009