Abstract: A suction irrigator, particularly for surgical use, is made as two units of plastics material. One unit is formed by a handle having first and second parallel bores which are coupled respectively to a suction source and a source of irrigating fluid. The other unit comprises a valve assembly the housing of which is formed by injection moulding. The valve assembly has two inlet conduits which are inserted within respective bores in the handle, and an outlet conduit which can be connected to one or the other of the inlet conduits by displacing a valve member. The bores extend along tubular formations in the handle which are linked along most of their length by a land but which are separated by a slit close to the valve. On the handle there is a lip positioned to engage a resilient catch on the valve member and thereby limit its displacement.

Abstract: A fuel-gauging system has a capacitive probe mounted in a fuel tank and supplied with an alternating voltage V.sub.s from a drive unit. The output of the probe is rectified by a diode mounted in the tank, prior to supply to a measuring unit. The voltage V.sub.D across the diode varies with temperature and is measured periodically by reducing the input voltage V.sub.s by a known factor X. The voltage V.sub.D is calculated by the measuring unit from the two output currents I.sub.1 and I.sub.2 produced respectively at the two different voltages V.sub.s and V.sub.s /X. The capacitance and hence the depth of fluid is calculated using the known voltage V.sub.D across the diode. The drive unit has a transformer that is used to reduce the voltage periodically by switching between different tappings of its secondary windings.

Abstract: A radiation pyrometer for a gas-turbine engine has a sapphire lens that focusses radiation from the turbine blades onto the end of a fibre-optic cable. The front, exposed surface of the lens has a vapor deposited layer comprising a mixture of platinum and aluminum oxide which acts as a catalyst to promote oxidation of soot to a gaseous form and thereby reduce contamination of the lens.

Abstract: A tire pressure sensing system has a sensor mounted on the tire hub, the sensor having a mask that is moved on change in tire pressure. Two rows of fibres at the end of a fibre-optic cable are positioned on opposite sides of a slit in the mask. The fibres of the two rows extend along a central core and an outer ring respectively of the cable. The rear end of the cable is mounted coaxially of the tire in alignment with a stationary cable having an inner core and an outer ring which extend to a radiation source and to a detector respectively. The source supplies radiation, via the cable, to the outer ring of the cable and hence to the row of fibres. Change in pressure moves the mask, thereby changing the amount of radiation received by the other row of fibres which passes to the outer ring of the stationary cable and thereby to the detector. The detector monitors the radiation and provides an output indicative of tire pressure.

Abstract: An improved door gasket comprises a snap base having a pair of oppositely facing flanges. Running along the web of the snap base between the snap flanges is a pair of catches which each mate with a complimentary one of a pair of depending latches on a snap channel when the snap channel is pressed against the snap base. A strip of elastomeric gasket material is wedged at each of its lateral edges between a separate one of the snap base flanges and the snap channel flanges to form a half rounded deformable sealing body. Although the snap channel is thus firmly held to the snap base by the engagement of the snap base catches and the snap channel latches, easy separation of the snap base and snap channel is accomplished by simply prying the snap channel from the snap base to facilitate gasket strip replacement.

Abstract: A Mach airspeed indicator instrument has a pointer that is rotatable around an airspeed scale and a Mach scale, the Mach scale itself being rotated in response to altitude change. A marker can be rotated around the scales via a cam that is manually rotated by an external knob. Rotation of the Mach scale is coupled via two vertical links and a lateral arm to rotate a gear ring which carries a peg. When the gear ring reaches a certain position the peg contacts and displaces a similar peg which rotates the marker with the Mach scale. The Mach value at which this occurs is adjusted manually from outside the instrument by a knob. Twisting the knob causes a vertical displacement of a mounting bracket on which the lateral arm is pivotted. The lateral arm is fixed at the end coupled with the Mach scale so that it rotates about that end causing rotation of the gear ring without affecting the Mach scale.

Abstract: A substrate for a leadless chip carrier is formed on a rigid multi-layer circuit board. Layers of copper-clad invar are secured to opposite sides of the board, and on top of these are mounted respective layers of elastomeric material. An electrically-conductive layer is laid on top of the upper elastomeric layer and this is formed in a pattern of contact elements, and tracks which may be of dog-leg shape and which are interconnected to other layers of the substrate by plated holes. The chip carrier is supported on a heat transfer pad of copper which rests on the upper invar layer and is secured thereto by a layer of solder. The pad may have an integral pillar that extends through a copper-plated aperture in the substrate to a heat-dissipating pad on the surface of the lower elastomeric layer. Contact pads on the chip carrier are soldered to the contact elements, the height of the heat-transfer pad being such as to separate them and ensure a thick solder joint.

Abstract: A valve has a tubular housing with two inlets spaced apart along its length, and a single outlet intermediate the inlets on the opposite side of the housing. One end of the housing is closed, its other end being open. The first inlet, close to the open end, is connected to a source of reduced pressure; the second inlet opening, close to the closed end, is connected to a source of raised pressure. A valve member is displaceable along the housing, being urged to the open end by a spring. First, second and third dished flanges are mounted coaxially on the valve member. The three flanges are spaced such that the outlet is connected to the second inlet when the first flange is located between the outlet and the first inlet, and the other two flanges are located between the open end of the housing and the second inlet.

Abstract: A regulated compressed air source supplies compressed air to a plurality of individual hand dryer stations where an air moving device such as an ejector or venturi operable heat exchanger to a user. In the preferred embodiment, the heat exchanger of each station uses hot water circulated by a pump from a common reservoir to warm the air.

Abstract: A Mach/airspeed indicator instrument has two pressure capsules each of which have a finger projecting from one face which is displaced by deflection of the capsule. Each finger is coupled to a respective arm that extends radially from respective shafts, so that displacement of a finger causes rotation of the respective shaft about its axis. Rotation of one shaft causes rotation of a Mach scale plate whereas rotation of the other shaft causes rotation of a pointer around an airspeed scale. The rear end of the Mach shaft is rotatably mounted at one end of a radially-extending lever that is in turn pivotally mounted close to its other end. The airspeed shaft is coupled with the Mach shaft by means of a link that extends between a plate fixed to the airspeed shaft and the lever. Rotation of the airspeed shaft thereby causes rotation of the lever and lateral displacement the Mach shaft about a pivot point at the end of the finger.

Abstract: An epidural filter for connecting intermediate a syringe and an epidural cannula has a two-part housing formed with an inlet and an outlet. Within the housing a filter membrane is supported, parallel with the direction of fluid flow through the filter, by struts located on opposite sides of the membrane. Fluid is supplied to the filter from the syringe via a female Luer-tapered bore and distributed over the filter membrane along a channel and passages between the struts. The filter has an outlet coupling comprising a nose, having a bore, around which extends a screw-threaded collar. A clamping head is screwed into the collar about the nose so that the nose bears on a resilient bush contained within the head. The bush has a bore which receives the cannula so that when the clamping head is screwed onto the housing it forms a fluid-tight seal between the cannula and the housing.

Abstract: A gyroscope motor control system has a phase-locked loop circuit and an antihunting circuit. The phase-locked loop circuit has a voltage-controlled oscillator which produces the drive signal for the motor. The frequency of the oscillator is controlled by the output of a phase discriminator which is in turn dependent on the difference in phase between a reference frequency and a feedback signal from the motor drive signal. A capacitive pick-off senses the speed of rotation of the gyroscope inertia wheel and a signal in response to this speed is supplied to a directional phase discriminator together with the feedback signal. The output of the discriminator varies with change in phase difference between its two inputs, and is supplied via a switching transistor to the input of the oscillator to effect minor variations in its frequency such as to reduce fluctuations in motor speed. The transistor is held off until there is substantial synchronism with the motor drive signal and the inertia wheel speed.

Abstract: A fuel-gauging system has a capacitive probe comprising an outer tubular electrode and a coaxial inner electrode. The outer electrode is supplied with an alternating signal from an oscillator, the inner electrode being connected to a detector unit via a resistor. The resistor is mounted between the electrodes about midway along the length of the probe, the resistor having a value that is selected to give a substantially linear output of the probe and is at least 0.1 of the reactance of the probe, preferably being about 0.3595 of the reactance. The resistor may be connected to a phase-sensitive circuit that is controlled by a phase-shift circuit which receives the input signals to the probe and shifts their phase by 90.degree., so as to produce an output that is in phase with the probe output. In this case the value of the resistor is preferably 0.2178 of the probe reactance.

Abstract: A radiation pyrometer, or other optical sensor, has a mirror assembly capable of withstanding high temperatures. The mirror assembly is a block of a steel containing between 15 and 20% chromium, 4.0 and 5.2% aluminium, 0.05 and 0.4% yttrium, 0.2 and 0.4% silicon, and 0.00 and 0.03% carbon. A reflective surface on the assembly is provided by an aluminium oxide layer. The assembly is formed by heating a body of the steel such as to produce the aluminium oxide layer which is then polished to a reflective finish. After heating, the body is machined to the desired shape of the mirror assembly.

Abstract: A capacitive fluid-gauging probe has a tubular electrode that is secured at its upper end to the wall of a reservoir by an integral mount moulded from a frangible plastics material. The mount has a collar that is fitted to the probe and from which extend radially three pairs of struts. The struts are joined at their outer ends with respective pillars that extend parallel to the probe. The pillars are joined with a plate that is secured to the wall of the reservoir above the probe. Domed plugs are inserted in both ends of the electrode to protect the wall of the reservoir which may be of flexible material. Preferably the ends of the probe are spaced from the reservoir walls. In operation, excessive force on the probe causes the struts to break, thereby allowing the probe to be displaced within the reservoir.

Abstract: Apparatus for measuring mass flow or density of fluid has a turbine mounted resiliently by torque rods within the fluid-flow line. The turbine has a number of vanes that extend radially to define passages parallel to the flow of fluid in the fluid-flow line. A torque driver causes oscillatory rotation of the turbine so as to give fluid in the passages a component of displacement at right angles to the passages. The turbine is driven simultaneously at two frequencies, displacement being sensed by a pick-off. The first frequency f.sub.90 is adjusted so that a 90.degree. phase difference is produced between the drive signal and the turbine displacement--the density of fluid being derived from this frequency. The second frequency f.sub.D is a fixed fraction F of the first frequency, the phase difference between the second frequency and turbine displacement being used to derive an indication of mass flow.

Abstract: An oil-level detector is mounted on the outside face of a glass window in the wall of an oil tank. The detector has two fibre-optic cables which extend within a cavity between the detector and the window. The ends of the cables are mounted one above the other, one cable transmitting a beam of light at an angle .alpha. of 60.degree. to the window, through an oil in the cavity which has a refractive index substantially equal to that of the window glass. The angle .alpha. is greater than the critical angle of glass with air, and less than the critical angle of glass with the oil in the tank. When the window is covered by oil in the tank the light is refracted into the tank. When the oil level falls below the window, the light is reflected to the other cable which is connected to a control unit. The control unit gives a warning a predetermined time after the level has fallen.

Abstract: A gyroscope inertia ring torquer has an inertia ring formed of an annular sleeve of magnetic material around which are mounted two annular permanent magnets. The permanent magnets produce radially directed fields of opposite polarities. The torquer also has four fixed electrical coils equally spaced outwardly of the inertia ring around a portion of the gyroscope casing, of a magnetic material. The coils are arranged, when energized, to produce radial magnetic fields which interact with the fields produced by the permanent magnets and thereby apply a restoring torque to the inertia ring. The permanent magnets are spaced from one another such that the torque produced by the interaction of the magnets with the casing is a minimum.

Abstract: An igniter test unit produces a square wave voltage that is applied across a parallel circuit comprising a first capacitor and a series arrangement of a second capacitor and diodes. An inductance and a thyristor are connected across the first capacitor, in series. When the thyristor is rendered conductive the voltage across the diodes becomes the sum of the voltages across the capacitors, this voltage being applied across the igniter. Switching of the thyristor is controlled such that the voltage is applied to the igniter in increasing steps of 25 volts until the breakdown occurs at the same voltage five times in succession. The voltage across the igniter is determined by applying it across a capacitive divider, one capacitor being discharged in steps, and the number of steps required to reduce the voltage to a reference value is counted.

Abstract: A motor driven winding mechanism suitable for a vehicle panel or the like, said window being movable by means of a raising and lowering mechanism (41) having an operating shaft (50) thereon which is rotatable to effect raising and lowering of the window, includes a reduction gear unit (10-30) drivingly coupled to the motor and to be mounted on the operating shaft for rotating that shaft, and sensing means (52-62; 72-80) for sensing rotation of the gear unit about that shaft due to reactive torque produced in the gear unit during operation and controlling operation of the motor in accordance therewith, for example, by de-energizing or reversing the motor upon a predetermined rotation being sensed. The sensing means senses predetermined displacement of the reduction gear unit around the operating shaft axis against the action of a spring (60, 80) resulting from reactive torque produced therein.