A filter element for straining liquid formed of a filter material in a convoluted form including two portions, one portion being a planar portion and the other portion being a corrugated portion having a plurality of elevated areas. The filter material is foled in half in the longitudinal center and wound in convolutions so that a series of letters V are formed on a transverse cross-sectional surface thereof. The pitch of the elevated areas is smaller in the central portion of the convoluted filter element corresponding to the end of the filter material at which winding is started and larger in the outer peripheral portion thereof.

A strip of filter material is folded so as to form two closely adjacent strip portions which are of one piece and have aligned longitudinally extending free edges and longitudinally extending second edges transversely spaced from the free edges and unitary with one another. The strip is coiled so that each of the strip portions forms a plurality of convolutions which alternate with the convolutions of the other strip portion. Means is provided in the region of the second edges for preventing liquid being filtered from forcing contaminant particles through the filter material.

A method of making a liquid filter includes the steps of providing a spiral roll of filtering material on a central tubular member, providing a housing member into which the roll is to be placed and laying a bead of thermoplastic material having a given softening point on an outer surface of the roll at least around the circumference of the roll close to an end thereof. The bead is pressed with cooled forming jaws, while in a warm state, to suitable dimensions corresponding to inside dimensions of the housing member. The housing member is heated to a temperature above the softening point of the thermoplastic material, the roll is inserted into the housing member and thereafter, the housing member is cooled. The thermoplastic material cools, acts as a glue and constitutes a tight, rigid connection between the housing member and the roll of filtering material.

A filter including a first flow path having a plurality of interconnected channels and a second flow path having a plurality of interconnected channels. The channels of the first and second flow paths are alternatingly configured in a substantially concentric pattern. A filter media is interposed between the channels of the first and second flow paths. A filter including a filter media arranged in a plurality of substantially concentric layers; a fluid outflow system contacting the entirety of one side of the filter media, and a fluid inflow system contacting the entirety of an opposite side of the filter media. A method of filtering a fluid including the steps of flowing the fluid along an inflow path having a fluid permeable core member in fluid communication with a plurality of inflow channels via an inflow conduit extending radially outward from the core member, passing the fluid through a filtration media, and collecting the fluid within an outflow path having a plurality of outflow channels in fluid communication with an outflow conduit extending radially inward toward the core member. The inflow and outflow channels are alternatingly configured in a substantially concentric pattern and have the filtration media disposed therebetween.

A filter (200) filters fluid flowing along an axial flow direction (14) and includes a plurality of panels (206, 208, 240, 242) of pleated filter elements (44), each filter element having a plurality of pleats defined by wall segments (50) extending along a transverse direction (210) between first and second sets of pleat tips at first and second sets of axially extending bend lines (46, 48), the transverse direction (210) being perpendicular to the axial direction (14). Each of the panels (206, 208, 240, 242) extends along a lateral direction (212) perpendicular to the axial direction (14) and perpendicular to the transverse direction (210). The wall segments (50) extend axially between upstream and downstream ends (52, 54), and define axial flow channels (55) therebetween which are alternately sealed at the upstream and downstream ends. Transverse gaps (214, 236, 238, 244, 246, 248) are provided between panels and the housing at upstream and downstream ends (52, 54), providing additional fluid flow axially therethrough and equalized contaminant passages.