| 摘要 |
A shaft seal comprising a sealing element (2), a rotary sealing part (4) mounted coaxially with the sealing element and forming therewith a contactle ss primary seal between opposed faces of the sealing element (2) and rotary sealing part (4) to substantially prevent fluid flow across the primary seal from a high pressure radial side to a low-pressure radial side, a seal housi ng (8), an annular pusher disc (9) disposed about a forwardly extending sleeve portion (8a) of the seal housing and coaxially with the sealing element (2), biasing means (10) acting on the pusher disc (9) to urge the sealing element axially towards the rotary sealing part (4), and a first sealing member (12' ') disposed between the pusher disc (9) and the forwardly extending sleeve portion (8a) in communication with the high-pressure radial side to provide a secondary seal between the high-pressure and low-pressure radial sides. An auxiliary sleeve (20) is disposed around the sleeve portion (8a) coaxially therewith and the pusher disc (9) is biased by the action of the biasing mea ns (10) against the auxiliary sleeve (20). This sleeve is maintained in sealing contact with the sleeve portion (8a) by the first sealing member (12'') and in sealing contact with the sealing element (2), either by direct content or by means ofa second sealing member (12'). The auxiliary sleeve (20) becomes deformed under high operating fluid pressures in a manner conforming with th at of the sleeve portion (8a), thereby reducing the risk of the sealing member (12) being blown out.
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