Abstract: A filter, especially a filter for lubricating oil of an internal combustion engine, including an inlet for the raw liquid and an outlet for the clean liquid. A filter insert (12) is arranged inside the filter, as well as a valve, such as a pressure relief valve (23). Parts of the valve are provided with coatings, for example hydrophobic coatings of polytetrafluoroethylene or silicone. The filter can also contain a heating element (34) in the vicinity of the valve.

Abstract: A filter device with a preferably hollow-cylindrical, pleated filter element which is arranged concentrically around a cylinder axis and through which a medium to be filtered passes. Seals are necessary on the filter device so that the medium to be filtered will not be able to leak out and so that the filter element, which typically is constructed of filter paper, must be fixed in place together with its pleats. Advantageously, an elastic composition can be disposed as a seal on at least one of the ends of the filter element, and after curing the elastic composition will fix the pleats of the filter element and will have sufficient residual elasticity to seal the filter element with respect to a central mounting tube on which it is to be mounted.

Abstract: A filter arrangement formed with a housing and a center tube connected with the housing. In the filter arrangement, a metal-free filter cartridge is arranged which includes an accordion-folded, annular filter element. The filter cartridge is provided with end plates on the axial end faces of the annular filter element, at least one of the end plates having an elastic construction, and each elastic end plate is provided with a flexible supporting ring which is arranged directly adjacent a radial seal formed by the elastic end plate.

Abstract: A receiver of ultrasonic pulses having a known pulse width and at a known spacing includes a gate which is normally conditioned to accept the ultrasonic pulses. When the first pulse is received, however, the gate is opened thereafter only when subsequent pulses should be present and is closed when no pulses are expected. Such an arrangement prevents multipath signals being interpreted by the receiver as information.