| 摘要 |
The present specification discloses an adjustable element for use in a filter or valve. The element comprises a coiled spring, tension or compression, which can be extended or contracted by suitable means to vary the degree of filtration and flow-through cross-section. The present invention provides an adjustable element with the individual spring coils having a generally square or rectangular transverse cross-section, the surface of the coils being surface-hardened. The interengaging surfaces of the individual coils can be flat so that the coils engage squarely, or curved for tangential contact. The smooth outer and inner surface of the element reduce the rate of filter cake build-up, and together with the surface hardening, facilitate the accurate control of the adjustment of the element. |
