| 摘要 |
A valve closure is described for use in particle separation apparatus. The closure is adapted to move in a direction to make sealing contact with a valve seat to create a closed chamber at the lower end of a frusto-conical cyclone separation chamber in which particles will collect during use. The closure is also adapted to move further in the same direction after sealing engagement has been effected, under the influence of any increase in suction created by restriction of the inlet to the apparatus. This reduces the gap between the downstream end of the frusto-conical cyclone separation chamber and the closure or a member carried by the closure, in response to any increased suction, whilst maintaining the sealed condition. The reduced gap enhances separation during the increased suction. The additional movement of the closure may be effected by providing an O-ring seal which is engaged by the closure to effect the sealing engagement. The O-ring is formed from resiliently crushable material so that a good airtight seal is effected by initial contact, but if the suction force acting on the closure increases, further movement of the closure is still possible to the extent to which the material forming the seal will crush. The resilience of the seal material controls the extent to which the closure is able to move, therefore the cross-section of the O-ring seal is selected so that there is at least sufficient crushable material in the cross section to accommodate the desired movement before the seal becomes incompressible. Alternatively a rubber O-ring seal is located on a resiliently deformable support member, which may be a ring and which is sandwiched between the O-ring and an annular seating in the wall of the chamber which is to be closed by the movement of the closure into contact with the O-ring. Thus after sealing contact has been established, subsequent movement of the closure is substantially accommodated by compression of the support member. Alternatively an O-ring seal is carried by a rigid annular support and an annular resiliently deformable member is sandwiched between the rigid support and the wall of the chamber.
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