Method of forming high load self-cleaning helical spring filters

Abstract

A method of manufacturing self-cleaning spring filters and at least two different spring filters are disclosed. One filter formed by the method comprises a helically grooved hollow mandrel with holes in the grooves and a helical spring closely fitted therearound. The pitch of the spring convolutions is opposite to that of the mandrel grooves so that the mandrel provides lateral support to the spring equivalent to that provided by a solid cylindrical bar for maintaining uniform diameter and concentricity of the spring convolutions while eliminating lateral displacement thereof during high load operations. While this one filter is secured at its bottom to the well, a modification requires securing thereof only at its top to the well with a packer. Further, full width spacers are formed on the spring convolutions for precise separation thereof and for preventing twisting and lateral displacement of the individual convolutions and for prevention of any variation of the gauge between the adjacent helical spring convolutions particularly while under magnified loads. One type spacer is a jog in the convolution and another is formed integral thereto.