Tubular filter and method of making the same

Claim 1

The method of forming a reinforced tubular element for a filter from a first strip of fine mesh metal screen and a second strip of perforated metal reinforcement having a width substantially equal to the width of the first strip which comprises, arranging the two strips in linear overlying relation with the opposite marginal side edges of one of said strips superimposed on and aligned laterally with the opposite marginal side edges of the other of said strips, advancing said two strips through a fixed guide means for maintaining the marginal side edges of the two strips in said overlying aligned relationship, causing said guide means to direct said two strips in said overlying relation onto a rotating, electrically conductive, cylindrical mandrel at an oblique angle to the axis of rotation of the mandrel, simultaneously moving the mandrel axially Relative to the guide means in a direction parallel to the axis of rotation of the mandrel while the strips are being fed thereon through said guide means so that the linearly superimposed strips are helically wound on the mandrel to progressively form a tube thereon which is supported by and axially advanced by and with the mandrel and with the overlying, laterally aligned edges at one marginal edge of one convolution of the two strips overlapping the overlying, laterally aligned edges at the opposite marginal edge of the preceding convolution whereby to form a helical seam around said tube between axially successive convolutions of the two superimposed strips which comprises four radially stacked edge portions of the two strips alternately interleaved, then progressively compressing said four radially stacked edges between said mandrel and an axially fixed seam welding wheel arranged tangentially to the mandrel with its axis inclined to the axis of rotation of the mandrel it substantially the same oblique angle as the guide means so as to track said helical seam as the tube and mandrel rotate and advance axially together and conducting a welding current through said four radially stacked edges between said seam welding wheel and said mandrel to fuse all four of said radially stacked edges together along the helical seam of the tubular element.

Claim 2

The method of forming a reinforced tubular element for a filter from a first strip of fine mesh metal screen and a second strip of perforated metal reinforcement having a width substantially equal to the width of the first strip which comprises, arranging the two strips in linear overlying relation with the opposite marginal side edges of one of said strips superimposed on and aligned laterally with the opposite marginal side edges of the other of said strips, advancing said two strips through a fixed guide means for maintaining the marginal side edges of the two strips in said overlying aligned relationship, causing said guide means to direct said two strips in said overlying relation onto a rotating, electrically conductive, cylindrical mandrel at an oblique angle to the axis of rotation of the mandrel, simultaneously moving the mandrel axially Relative to the guide means in a direction parallel to the axis of rotation of the mandrel while the strips are being fed thereon through said guide means so that the linearly superimposed strips are helically wound on the mandrel to progressively form a tube thereon which is supported by and axially advanced by and with the mandrel and with the overlying, laterally aligned edges at one marginal edge of one convolution of the two strips overlapping the overlying, laterally aligned edges at the opposite marginal edge of the preceding convolution whereby to form a helical seam around said tube between axially successive convolutions of the two superimposed strips which comprises four radially stacked edge portions of the two strips alternately interleaved, then progressively compressing said four radially stacked edges between said mandrel and an axially fixed seam welding wheel arranged tangentially to the mandrel with its axis inclined to the axis of rotation of the mandrel it substantially the same oblique angle as the guide means so as to track said helical seam as the tube and mandrel rotate and advance axially together and conducting a welding current through said four radially stacked edges between said seam welding wheel and said mandrel to fuse all four of said radially stacked edges together along the helical seam of the tubular element.