GB1070557A - Limited leakage shaft seal - Google Patents

Abstract

1,070,557. Mechanical seals. P. C. STEIN. Nov. 24, 1964 [June 1, 1964], No. 47816/64. Heading F2B. In a fluid seal for a rotary shaft 14 comprising a seal ring 20 axially movable by fluid pressure acting on opposed surfaces thereof and having a sealing face 22 which co-operates with a sealing face 18 of a runner 16 on the shaft to form a gap 50 therebetween through which limited leakage occurs from the high pressure side 12 to the low pressure side 48 of the seal, the pressure drop across the gap is made non- uniform by providing a shoulder 54 on the face 22 whereby the thickness of the gap between its high pressure extremity 52 and the shoulder 54 is greater by the offset amount 58 than the thickness between the shoulder and the low pressure extremity 51, the offset 58 being between 0À0001. to 0.001 inch. The ring 20 is sealed by an 0-ring 30 to a cap 24 secured to the shaft housing 10 and is prevented from rotating by pins 36 on the cap engaging recesses 38 in the ring. In operation, the ring 20 automatically occupies an axial equilibrium position with a predetermined gap thickness depending on the pressure differential across the seal. The gap thickness may be from 0.0002 to 0.002 between 52 and 54. In order to close the gap 53 when the pressure differential is small, the ring 20 is urged towards the face 18 by springs 40. In a modification (Fig. 3) the shoulder (92) is formed by an insert (90) housed in a recess (86) in the ring (80) and projecting therefrom by an amount equal to the height of the shoulder.