Abstract: An ultrasonic power meter is provided for measuring ultrasonic power emitted by a device (18) under test. The meter includes a casing forming a chamber (16) within which an ultrasonic absorber (14) formed from polyurethane material is located. Overlying the absorber (14) is a membrane (12) of polyvinylidene fluoride which acts as a pyroelectric detector. The meter also includes a transfer medium (10), typically water, for allowing the transfer of ultrasonic energy emitted from a device (18) under test to the meter.

Abstract: A cavitation sensor includes an ultrasonically absorbent coating (20) disposed around a piezoelectric element (30) and a conduit (25). The conduit (25) includes a boundary delimited by the piezoelectric element (30), while the ultrasonically absorbent coating (20) is substantially transparent to acoustic driving field frequencies. The sensor is more accurate than prior art sensors.

Abstract: A tracking system is provided for tracking while determining the position of a point relative to a datum and includes a carriage (4) rotatably mounted on a frame (1) and which can rotate around a precision sphere (2). An interferometer (16) is mounted so as to rotate with the carriage (4), such that a mechanical center of rotation of the device and the measurement datum of the interferometer coincide at the same point.

Abstract: A radiation resistant meter for use in intense ionising radiation fields ludes a meter unit (10) coupled to a separate processing and indicating unit (50) by means of a radio link (24,35). Radiation sensitive components in the voltage amplifier (14) and low frequency oscillator (16) are replaced by valves. Certain radiation sensitive components are covered in a potting compound. A calibration system formed from five zener voltage references (28) is located close to the sensor (12) and coupled to the same circuitry by a multiplexer (30), as is a thermistor (24) the signals from the components (12,26,28) are fed to the amplifier (14) in cyclical manner and processed by a computer (40) in the receiving unit (50). From the calibration voltages (28), the computer determines a calibration curve used for determining the magnitude of the parameter sensed by the sensor (12). The meter can operate at and measure radiation levels far higher than previously known equipment.

Abstract: A source of seismic waves operable within a borehole filled with liquid crises a module supported by a cable. The module includes means to generate a high voltage and to charge a bank of capacitors, and means to connect the capacitors across a pair of electrodes forming a spark gap. The electrodes are immersed in liquid at the same pressure as the borehole liquid and acoustically continuous with it, and are separated by a gap of width between 0.5 and 20 mm. If the gap is greater than about 5 mm, both the electrodes should be covered with insulation except at the positions where the spark is to be formed. The module can operate automatically at considerable depths and at high pressures.

Abstract: A heat exchanger including a plurality of fluid pathways (13, 15, 16, 17, ) in which at least some are defined between surfaces of unperforated primary plates (10). Between the primary plates (10) are at least two secondary perforated plates (12) extending along the fluid pathway (13, 15, 16, 17, 18) with perforations (11) in adjacent plates (12) being staggered. Adjacent secondary (12) and primary (10) sheets are in contact such that conducting pathways (19) are formed extending between the two primary surfaces while areas of secondary plates (12) not in contact with other secondary plates (12) constitute secondary surfaces (22).

Abstract: Disclosed is a device for lifting a single layer of fabric or fiber reinfed plastic sheets from a stack of such sheets with minimal damage to the structure of the fabric. A frame and a flexible base plate are provided with a plurality of individual needle gripper devices located at opposite ends of the base plate. Each needle gripper device includes a needle of arcuate form rotatably mounted about an axis of its arc so that when the needle rotates, the tip of the needle will penetrate a fabric sheet upon which the apparatus is placed and then roll the sheet relative to the frame so that the sheet is peeled away from its original position without stretching or deformation of the fabric.

Abstract: A stabilized helium-neon laser emits radiation in the ranges of ultra-violet, infra-red and visible other than red in at least two modes. A stabilizing system consists of an alignment heater (19) which bends the laser tubes toward optimum alignment, a coil heater (20) which cyclically varies the tube length and permanent magnets (24,25) which reduce instability of mode polarizations and to optimize relative intensities of the modes. The transmitted output is stabilized in frequency by control of the laser tube length, with the stabilization signal derived from the steady or varying intensity of intensities of one or both of two orthogonally polarized optical outputs. There are many potential uses for non-red helium-neon lasers in applications where non-red light is required, for example, in multi-wavelength interferometry.

Abstract: In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones and two loudspeakers which form the active elements of a noise control system. The microphone outputs are fed via amplifiers to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller and a synchrophased propeller, controlled by a synchrophaser. Thus the synchrophase angle is varied dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.

Abstract: A plain bearing slide system has a carriage mounted on a slide by use of bearing pads. Each bearing pad is coated with a layer of polymeric material having a convex surface, and is arranged to ride on a counterface. The combined thickness of the layer and a layer providing the counterface is such that the difference between the static and dynamic coefficients of friction is substantially less than the difference associated with the material when used in bulk bearings. A slide system using PTFE, and with a combined thickness of the layers of 2 to 3 micrometers, operated as a measuring instrument under ambient conditions such that the PTFE is substantially non-eroding, has proved capable of providing measurements to an accuracy of 0.05 nanometers.

Abstract: A combined spring and damper comprises a plurality of spring elements (1), each of zig-zag form, disposed in radial planes with respect to a common axis. Also situated on the axis is a mass (7) of resilient material. When the spring is compressed along the axis the inward contraction of inner reflex portions (3) of the spring elements is resisted by the mass of resilient material, and the resulting axial movement of the radially inner reflex portions is resisted by contact with the mass of resilient material and axial compression thereof.

Abstract: A method of separating the constituent minerals of a mixture of minerals requires the introduction of fine particles of magnetic material such as finely ground particles of magnetite. The control of the zeta-potential of the minerals and particles of magnetic material provides heterocoagulation of the magnetized particles with one mineral but not the other to achieve separation. The method is ideally suitable for separating carbonates and phosphate ore and the separation process is enhanced by the addition of a surfactant such as oleate. The slurry is preferably subjected to low intensity magnetic separation to remove unattached particles of magnetic material which can be recycled to keep costs to a minimum.

Abstract: A fluid operated reciprocatable device has an outer, usually fixed, member nd an inner relatively movable member joined by a resilient member e.g., of rubber. The outer member is closed at one end so as to form an enclosure into which fluid under pressure can be admitted so as to displace the inner member in a given axial direction relative to the outer member. When a pulsating pressure is applied to the fluid the inner member vibrates axially in accordance with the pulses. The resilient member is proportioned so that its dimension in the axial direction is large in comparison with the thickness between the outer and inner members, e.g. 4 times larger. The properties of the resilient member are chosen so that it acts not only as a seal between the outer and inner members to contain fluid, but as a return spring whereby the inner member is returned, between fluid pulses, from an axially displaced position.

Abstract: The invention concerns an apparatus for collecting solids from the bed of a iquid or for establishing an anchorage in the bed of a liquid. The apparatus comprises essentially a substantially hollow structure into which solids from the liquid bed are induced as solids in liquid suspension. In the case of the apparatus being used for the collection of solids the structure is raised to the surface of the liquid for the solids to be harvested. When the apparatus is being used as an anchoring device the design is modified such that as solids from the liquid bed are induced into the substantially hollow structure they fill or partially fill the structure when then proceeds to bury itself into the liquid bed thereby establishing an anchorage.

Abstract: A respirator which is in the form of a protective hood is arranged to fit er the head including the face of a wearer, leaving a space between the hood and the wearer's head. A sealing member is provided between the hood and the back and sides of the wearer's head with means normally fitted within the hood to supply filtered air which can pass over the wearer's head and down over the wearer's face.