Abstract: Disclosed is a parallel filtering circuit comprising at least two filters of a depth layer filtering type connected in parallel to each other in conduits showing different fluid resistances respectively, whereby, even when both the filters are clogged with particles of contaminants, the total flow rate may not decrease sharply, so that a preventive measure can be immediately taken before a fatal situation occurs. An orifice may be connected at its inlet to the outlet of the conduit having a smaller fluid resistance and at its outlet to the outlet of the conduit having a having fluid resistance.

Abstract: A filter of depth layer type comprises a generally cylindrical filter body formed by laminating filter elements each in the form of a thin sheet of a filtering material having a central hole, and these central holes provide a conduit extending in the axial direction through the filter body. The filter body has a density distribution in which the density is lowest at the outer peripheral area sewing as an inlet for a fluid to be filtered and becomes progressively higher toward the conduit to serving as an outlet for the fluid to be filtered.

Abstract: A lubrication monitoring apparatus for a machine, in which an oil pressure gauge detects the pressure of lubricating oil of the filter, a first oil thermometer detects the temperature of lubricating oil before lubricating the mechanical section, a second oil thermometer detects the temperature of lubricating oil in the vicinity of the outlet of the lubricated mechanical section, and a warning device gives warning when any of the oil pressure, oil temperature, and oil temperature difference is out of a predetermined range.

Abstract: A filtering apparatus for removing impurities out of a lubrication oil for use in an internal combustion engine including low and high density filters having inlets commonly connected to an inlet conduit through which the lubrication oil to be filtered is supplied, an orifice arranged in an outlet conduit of the low density filter to produce a reduced pressure due to a fast oil flow and a conduit connected between an outlet of the high density filter and the orifice. Due to the reduced pressure applied to the outlet of the high density filter, a part of the oil is effectively sucked into the high density filter.

Abstract: A filtering member made of a filtering paper or nonwoven fabric tape is folded into a V-shaped cross sectional configuration, absorbing agents are uniformly dropped into the folded filtering member, the filtering member is further folded to wrap the absorbing agents therein and finally the filtering member is twisted to form a filter medium in the form of a string. The absorbing agents may be active carbon, active kaoline, water absorbing resin, magnetized magnetic material or combinations thereof.

Abstract: A filtering member for use in a filter such as an oil filter for removing impurities of different sizes contained in a fluid such as a working oil in an oil pressure apparatus comprises a cylindrical body made of resilient or flexible and porous material such as fabrics, porous synthetic resin, etc, the porosity of the cylindrical body decreasing gradually toward a center thereof. The filtering member can be easily and inexpensively manufactured by winding or deforming a sheet like member made of resilient material having a uniform porosity over its thickness into a cylindrical body in such a manner that an outer portion is expanded or stretched, but an inner portion is compressed.

Abstract: The peripheral surface of a coil of a filter web wound about a hollow shaft is covered by a liquid impervious flexible coating, and the outer periphery of a first end of the coil is secured to a supporting disc so that when liquid to be filtered is caused to pass through the coil in the axial direction thereof, the convolutions of the coil near a second end expand radially outwardly to trap contaminants in the spiral gap. Purified liquid collected at the first end of the coil is discharged through the hollow shaft. The filter unit is constructed such that a number of units can be readily connected in series.

Abstract: Liquid containing contaminants is passed through a lamination of a plurality of filter papers and the quantities of the contaminants deposited on upper and lower filter papers are compared with each other to determine the degree of contamination of the liquid.