Method of making a liquid filter

A method of making a liquid filter having a filtering roll which is fastened to a housing part, is itself made of a spiral of filtering material wound on a central tubular member, and is to be axially traversed by a liquid to be filtered, the method comprising, in combination:

• a. providing a spiral roll of filtering material on a central tubular member,
• b. providing a housing member into which said roll is to be placed, said housing member defining an outer edge,
• c. laying a first bead of thermoplastic material having a given softening point on an outer surface of said roll at least around the circumference of said roll in the vicinity of an end thereof,
• d. pressing with cooled forming jaws said first bead in a warm state to an outside diameter larger than the inside diameter of said housing member,
• e. inserting the roll partly into the housing member so that the first bead engages the outer edge of the housing member,
• f. heating said housing member to raise its temperature above said given softening point of said thermoplastic material to soften said first bead on its circumference during further insertion of the roll into said housing member and, thereafter
• g. cooling said housing member to solidify said thermoplastic material;
• whereby a liquid filter is formed upon solidification of said thermoplastic material which acts as a glue and constitutes a tight, rigid connection between the housing member and the roll of filtering material.