| 摘要 |
1,266,401. Shaft seals. DEMAG A.G. 6 March, 1969 [17 May, 1968], No. 12002/69. Heading F2B. A rotary shaft seal for a turbine or compressor comprises first and second axiallyspaced radially-floating rings 3, 7 supplied with sealing fluid (oil) through an inlet 4, the rings being so constructed that the shaft clearance 16 at the first ring is less than, and increases on thermal expansion at a lower rate than, the shaft clearance 15 at the second ring to ensure that the leakage of sealing fluid through the clearance at the first ring is maintained less than the leakage of sealing fluid through the clearance at the second ring, which leakage at the second ring varies automatically according to the operating temperature of the shaft and the second ring. The floating rings 3, 7 are pressed apart by a spring 5 and interconnected by projections 25, the ring 3 being provided with cooling fins 26 which co-operate with a rotation-prevention pin 17 and the ring 7 being heat insulated by a sleeve 6 of synthetic resin. The ring 3 is made of a material having a coefficient of thermal expansion substantially corresponding to that of the material of the shaft 1 which is usually made of steel; the inner surface of the ring 3 may be provided with a thin layer of antifriction material and any oil which does escape through the clearance 16 into the gas space A discharges through an outlet 18. The ring 7 may be made of aluminium alloy or zinc alloy; when the operating temperature of the steel shaft and ring 7 rises, cooling of the seal is automatically regulated by the greater volume of oil which passes through the increased clearance 15 from the chamber B to the bearing space C, D and discharges through an outlet 12. In a modification, the ring 7 may be divided into three segments each having inner and outer parts made of materials having different coefficients of expansion; upon being heated leakage gaps are created adjacent the ends of each segment. In another modification, the ring 7 is undivided and is provided on its inner surface with recesses filled with a low melting point material which fuses out upon overheating. |
