A projecting screen for optical purposes which meets the stringent requirements for the reproduction of macroscopic as well as microscopic images in transmission operation. The object comprises providing a projection screen comprising several scattering media movable in relation to each other, by which projected images may be reproduced free of grain- and flickering- or scintillation effects, under simultaneous improvement of the resolution and the transmission qualities. The substance of the in...

A semiconductor device comprises a semiconductor element divided transversely into at least four zones which alternate in conductivity type. A control electrode is applied to a neighboring inner zone where this zone reaches to the outer surface of one of the outer zones through a perforation in the latter and metallizing is applied to this same surface but set back from the control electrode. The same outer zone has other perforations distributed therein and the neighboring inner zone extends as...

A spray device which can cover a wide variety of sized and shaped areas, and which can be easily adjusted to cover a desired area. In operation, the device stores inflowing water under pressure, and energy in the form of compressed air, in a pneumatic pressure tank and intermittently discharges the water through a nozzle at rates greater than the inflow rate. With each discharge cycle, the nozzle is automatically rotated to point in a slightly different direction and adjusted for pressure at whi...

To decrease the number of interconnections necessary between a central comparison and monitor unit and a plurality of student-operated keyboard units, each keyboard unit has a specifically assigned connection code, in the binary system, and is connected according to this code to the wires in a cable; the monitor unit includes a scanning generator, scanning the wires, in binary code; upon coincidence of the scanned code with the connection pattern of a keyboard unit, a transistor in the keyboard ...

A live storage system in which pallets stored on racks are moved from a feed to a discharge station by a transfer trolley travelling on tracks below the racks and having a platform for raising and lowering pallets from and onto the rack, the transfer trolley carrying an auxiliary trolley for raising the platform both the transfer trolley and the platform being operated by a first linear induction motor with a second linear motor operating in opposition to the first motor to position the transfer...

A camera for observing a selected area is concealed by a hollow dome-like member partially metallised to form a convex mirror from the point of view of an observer in the selected area, whilst allowing light to pass through the member from the area to the camera.

A culinary timer device comprising a timer mechanism of adjustable operating period incorporated in a cooking vessel or in the cover of such a vessel, a thermo-sensitive device arranged to initiate operation of the timer mechanism when the temperature of the vessel contents reaches a predetermined value, and means for indicating when the operating period has ended.

A gas mixer is disclosed which is used for mixing different gases in order to obtain a solid by sublimation or chemical reaction. The mixing is carried out in a mixing chamber having a uniform, substantially circular, cross section and a length depending on the particular application. Build up of the solid is prevented by injecting the gases to be mixed into the mixing chamber so that the combined flow in the duct, at its inception, is characterized by an axial flow of one gas surrounded by a sp...

A lightbox for display purposes, such as advertising, comprises a rigid back plate adapted to be secured to a support surface, a light source carried by the back plate, and a front fascia of clear plastics material which can be flexed and which is held in place in a curved attitude on the back plate by the engagement of fastening means between the fascia and back plate. The fascia comprises outer and inner panels which sandwich a photographic transparency therebetween. Flexing of the fascia for ...

A blank cartridge for training purposes in the form of an elongated case made of thermoplastic synthetic resin and forming a hollow simulated projectile and a powder chamber. The case is provided with weakening lines for providing a predetermined rupturing of the case in the form of external longitudinal grooves or slots extending from the tip of the simulated projectile over substantially the entire length of the projectile. The powder chamber is provided with a powder charge mass of at least 1...