A filter unit includes a body portion having a proximal end and a distal end. An engagement protrusion extends from the proximal end. The engagement protrusion includes a first portion that has a first radius of curvature and a second portion opposing the first portion that has a second radius of curvature that is larger than the first radius of curvature. A protruding retention surface is disposed on and extends radially outward from the body portion. The protruding retention surface is adapted to secure the filter unit in a filter head assembly.

A filter for gravity-fed applications, having filter media with a hollow center, the filter being generally prone to a degradation or cessation in fluid flow due to air entrapment or air lock within the filter housing cavity, which develops during filtering. A diffuser element is introduced to pierce the entrapped air bubble, the diffuser element being an elongated structure connected to the filter housing top end cap and extending through the entrapped air bubble to the filter media.

A filter apparatus has a filter housing (1) accommodating at least one filter element (17) having an inner filter cavity (23) enclosed by a filter medium (27). The housing (1) contains an element holder (19) that interacts with the filter element (17) located in its functional position. The element holder (19) has a projecting accommodating part (43) with an outer configuration adapted to the shape of an opening (37) located at the end of the filter element (17) to be secured to the element holder (19). The accommodating part (43) fits through the opening (37) of the filter element (17) located in the functional position.

A filter element for filtering liquids has a folded filter medium with outer fold edges and inner fold edges, wherein the inner and outer fold edges extend along a longitudinal axis of the filter element. A support body is provided with a first support body section and a second support body section, wherein the first support body section is facing the inner fold edges and hugs closely an envelope of the inner fold edges. An envelope of the outer fold edges and the second support body section hug closely at least sectionwise an outer circumferential surface of the filter element.

A filter for hydraulic fluids including a container defining inside a housing compartment fluidically communicating with an inlet and an outlet associated with and a filtering cartridge, and partitioning the compartment in first and second chambers. The cartridge is configured and positioned for determining the filtering of the hydraulic fluid from the inlet which flows from the first to the second chambers. The container exhibits an engagement portion projecting inside the housing compartment and defining a collar having an outer coupling lateral surface, while the filtering cartridge exhibits a respective engagement portion defining a respective collar exhibiting an inner coupling lateral surface configured for engaging outside the outer coupling surface of the container. The coupling surface of the engagement portion of the container exhibits a polygonal cross-section; the inner coupling surface of the engagement portion of the cartridge is at least partially countershaped to the coupling surface of the container.

A membrane casing that watertightly houses a membrane element for filtering raw water includes a tubular casing main body, a lid body, and a pressing mechanism. The casing main body houses a membrane element. The lid body fits an opening end of the casing main body and is movable in the axial direction of the casing main body while maintaining the attitude and while securing watertightness with the casing main body. The pressing mechanism and presses the lid body to press and hold the membrane element housed in the casing main body. The membrane casing has a simple configuration capable of watertightly securing using a predetermined pressing force by accommodating variations in size of the membrane element, even if the membrane casing cannot be formed into a cylindrical shape.

An air filter mounting plate having sealing side and a filter media retaining side, said mounting plate including an air passage opening and a gasket encircling the air passage opening provided on sealing side of the mounting plate, the gasket comprising a connection portion and double sealing lips (7a,7b) extending from the connection portion, and wherein the gasket is joined with the mounting plate by the connection portion being fixed on the sealing side of the mounting plate.