The invention concerns a filter system having a plurality of individual removable filter units disposed between inlet and outlet ducts for a gas flow path to filter the gas flow. The system comprises one or more filter ports between the inlet duct (3,5) and the outlet duct (4,6) to receive removable filter units (1), a transfer port (25) co-operable with and sealable by a flask (20) for the filter units, a seal plate (14) removably located in the transfer port, means (15) for removing the seal p...

The invention relates to laser systems of the type comprising optical fiber amplifiers. A laser system comprises a first laser 1 and a second laser 2. The second laser 2 is pumped at a first wavelength .lambda..sub.1 and caused to lase at a second wavelength .lambda..sub.2. The first laser 1 has absorption bands .lambda..sub.1 and .lambda..sub.2. The output .lambda..sub.2 of laser 2 and the remnant pump at .lambda..sub.1 are coupled and both are used to pump the first laser 1, thus causing laser...

The invention provides a number of improvements useful in printers which may be of the fixed, portable or hand-held types. In one aspect, the printer, which comprises a housing, a printing unit, means for feeding to said printing unit a substrate onto which indicia are to be printed, means for feeding a thermal transfer ribbon to said printing unit, and means for providing electrical power to operate the printer, is characterized by means permitting independent movement of said substrate and sai...

Apparatus for improving properties of a solid material by providing shock waves therein. A laser oscillator 10a provides a plurality of pulses 112 of coherent radiation. The leading edge of each pulse is sharpened either by a metal foil 18 or by phase conjugation reflection means 18a, 18e including a stimulated Brillouin scattering cell 18d,18e and optionally a Faraday isolator 18b. Each pulse is directed onto an amplifier 123 comprising first and second laser amplifier rods 23a,23b in series. A...

A plug (P) is present in the bore (B) of a wedge gripping device (W) in a barrel (1) of a grip. The device (W) is formed of tapering segments (4) which are held apart by the plug (P). When a length of wire or strand element (E) is received in the device (W), the plug (P) is diplaced out of the bore (B) so causing the device (W) to grip the element (E).

A filtration system for extracting solids from a gas includes a separator having an inlet section and an expansion chamber. A filter is located in an upper portion of the expansion chamber. Two hingedly interconnected plate sections extend from the inlet section to the expansion chamber to control the convergence of the passage for gas in the inlet section and the divergence of the passage for gas in the expansion chamber.

A conveying system useful for synchronous conveying of articles along a straight line path between a driving and driven pulley. Selected teeth of a synchronous belt are modified to provide passages between a backing and a top land. Each modified tooth is formed with a reduced addendum. A tip plate is bolted to the top land of the modified teeth so that the height of the teeth become compatible with the standard size teeth of the belt. The tip plate bolts are also used to fasten transporting devi...

Rotating surveillance systems of the type which detect a moving object within a field-of-view and provide a representative image of the object may suffer from limited sensitivity when having a wide coverage. The system described herein detects and provides an identifiable image of a moving object within its field-of-view by forming an image of the object on a charge-coupled device and determining the rate of relative movement between the image and the device and hence using the rate of relative ...

A coal cutting machine 13, a conveyor 12 and a plurality of mine roof supports 10 extend along the face 11 of a coal mine. The operation of the hydraulic jacks of the roof supports are controlled by pilot valves which are electrically powered and rotationally driven. For example, motorized or cam operated pilot valves can be used. Such pilot valves use much less energy than valves controlled conventionally by solenoids, and the electricity supply can thus be at an intrinsically safe level. The o...

In a display system light from an object (14) is deflected on to a collimator (16) and superimposed on an external view through a combiner (10) from an observing position (11). Relay optics (17) in the path of light from the object (14) has spaced apart elements (L.sub.1,L.sub.2) which produce first and second exit pupils (P.sub.1, P.sub.2). Exit pupil volumes (V.sub.1, V.sub.2) overlap to give an extended field of biocular view. The restricted field of view associated with prior art display sys...