Abstract: A modular, self supporting flight of stairs, comprising at least one pair of stringer units for supporting at least one step thread. Each stringer unit comprises a vertical side plate provided with an horizontal, upper flange and a vertical front plate defining with the side plate, a rectangular dihedron. This front plate is also provided with an horizontal, upper flange defining together with the upper flange of the side plate, a rigid, L-shaped support very stable in use for supporting one end of the thread. Each stringer unit also comprises a small, fixation plate integrally extending the side plate in the same plane as, or in a plane parallel to, the plane of the side plate. The stringer units of each pair are fixed to the corresponding units of a pair immediately superior or inferior thereto by riveting or bolting the fixation plates of one pair to the side plate of the other pair through a plurality of holes punched fixation plate and the lateral plate of the stringer units for receiving the bolts.

Abstract: A compact apparatus for moving a set of X-ray films or film cassettes past a picture-taking station. The apparatus comprises a plurality of holders impervious to X-rays onto each of which are mounted two films in back-to-back relation. The holders are moved in a closed loop past a picture-taking station where they present one of their two films for a first picture. After exposure, the holders are moved through the loop a second time during which they are rotated through 180.degree. so as to present the other films they carry at the station for a second picture.

Abstract: A starter device for a single phase A.C. motor having a main winding and a starting winding disposed for connection to a single A.C. source. This starter device comprises a semiconductor switching device having a control electrode and a transconductive path, such as, for example a triac. This switching device is connected in series with the starting winding and the single A.C. source to energize or disconnect this starting winding. A magnetic detector is disposed between two adjacent poles of the main winding of the stator of the motor and has its axis of detection extending in the direction of the lines of magnetic flux forced out of the two adjacent saturated poles of the main winding during the initial inrush of current through this main winding upon starting of the motor.

Abstract: A system for raising and lowering an auxiliary retractable wheel train of a truck trailer to permit neutralizing the braking mechanism of the wheels of the auxiliary train when the latter rises. A selection valve for rising and falling of the auxiliary retractible wheel train cooperates with a relay slide valve which, according to whether it is opened or closed, allows or cuts off the flow of braking fluid in the piping across which relay valve is mounted.

Abstract: A panel for use in a sectional door. The panel which is easy to construct and has improved insulating properties, has an elongated insulating core, a first metallic skin on one face of the core and a second metallic skin on the other face of the core. The first and second metallic skins both have crimped edges that are joined together at the sides of the panel with an insulating member interposed between them. The insulating members on the long sides of the panel may include diverging seal arms projecting outwards for providing a seal between adjacent panels. The invention is also directed toward a sectional door incorporating the panels.

Abstract: An improved, foldable traction mat comprising a plurality of bars pivoted together to form a grid-like traction member when the mat is opened up for use. The bars pivot into generally parallel, closely adjacent position when the mat is folded up for storage.