Abstract: The device has a transmitting and receiving device for electromagnetic radiation which is arranged in the region of a bumper and includes an RF circuit arranged on a support plate and at least two substantially planar antennas that interact with the RF circuit. The antennas are fixed on a plastic sheet. A printed circuit board has perforations for the passage of radiation from the RF circuit to the antennas. Spacers having a precise longitudinal extent are inserted into the perforations, and the plastic sheet is bonded onto the underside of the printed circuit board such that the antennas each bear on a spacer.

Abstract: A split ring seal of a centrifugal pump comprises two rings that consist of a sintered material and that are respectively connected in a frictional or positive manner to a front cover disk of the impeller and to the pump housing which are made of a cast polyamide as produced by the activated anionic polymerization of monomeric laurinlactam.

Abstract: A soft protective construction for body protection, such as a bullet-proof vest or shirt is disclosed wherein a double layered bullet-stopping arrangement of mutually moveable rectangular or square protective plates is provided which plates can preferably be inserted into pockets of a carrier material. The outer layer of plates lying on the bullet impact side consists of steel and at least in portions thereof said outer plates are overlapped in scale-like fashion. The inner plate layer, which lies closer to the body than does the outer layer, is designed to absorb or largely destroy the impact energy of a striking bullet.

Abstract: An improved method for the production of castings by the anionic polymerization of lactams, particularly lauric lactam, in which two melts prepared separately, one with a catalyst and one with an activator, are polymerized together in a mold heated to substantially the same temperature as the melts, is described, the improvement comprising the application of a vacuum in the range from about 80 to 450 Torr, said vacuum being selected in accordance with the formula S.times. T= K where S is the surface area of the casting exposed to the vacuum, V is the volume thereof, T is the vacuum application time and is less than the polymerization time and K is a constant. Said vacuum is replaced by ambient pressure either progressively or instantaneously when the polymerization mixture reaches a highly viscous non-stirrable state. Thereafter, the polymer may be heat treated at a temperature about 10.degree. to 20.degree. C.