Abstract: A spring member for a piezoelectric type injector is manufactured from a rectangular shaped sheet material, by rolling it to form as a tubular shape. Both of circumferential ends of the rolled up spring member confront each other, but are not connected to each other. Multiple apertures are regularly formed in a wall portion of the spring member. Notches are formed at the confronting end portions of the spring member, wherein a pair of opposing notches form an opening, which is equivalent to the apertures formed in the wall portion. A distance between the confronting end and a side end of the aperture, which is closest to the confronting end, is made to be larger than “a/2”, wherein “a” is a distance between neighboring apertures formed in the wall portion.

Abstract: In a filter manufacturing method, during a time period from the start of the suction of the slurry to a point in time when fibers in the slurry accumulate on the outer peripheral surface of the protector to a prescribed thickness, the protector and its leg portions are held spaced away from each other. The leg portions are moved toward the protector so that the leg portions are disposed at a position spaced by a uniform distance from the outer peripheral surface of the protector and the suction operation is continued. Thus, the slurry containing the fibers therein can be easily caused to flow deeply into recess portions of a fin-like portion with no fiber being caught between the protector and the leg portions, thus reducing non-walled portions.