| 摘要 |
<p>A primary valve orifice (26) divides a check valve cavity into first and second portions (4, 6). A valve member (34) closes the orifice (26) in response to higher pressure in the first portion (4) and is unseated to open orifice (26) in response to higher pressure in the second portion (6). An axial passageway (44) extends through the valve member (34). A control rod (50) extends into the cavity (4, 6) and through the passageway (44). The rod (50) carries a secondary valve plug (52) that is biased by a spring (60) to close one end of the passageway (44), and a pull block (78) that engages the opposite end of the valve member (34). A stem (40) extends from the valve plug portion (36) of the valve member (34) through the orifice (26) and is telescopically received in a sleeve (62). The control rod (50) is pulled to cause the secondary valve plug (52) to unseat and the pull block (78) to engage the sleeve (62). This opens the passageway (44) to equalize pressure on the two ends of the valve member (34). Further movement of the control rod (50) moves the valve member (34) and sleeve (62) as a unit to open the orifice (26). The sleeve (62) may be omitted, with the pull block (78) directly engaging the valve member (34). <IMAGE></p> |
