| 摘要 |
The invention relates to a safety valve for an oil well, allowing an operation in artificial throughput mode. This valve comprises, at its upper part, a fastening sleeve 309 for fixing a tube for supplying injected fluid and an anchoring system including movable dogs 54 and a sheath 55 for locking the said dogs in the anchoring position. The valve in accordance with the invention is characterised in that it is provided with an upper unlocking sleeve 500 fixed into the fastening sleeve 309 by shear screws. Unlocking takes place by blocking off this sleeve by means of a ball 505 and by establishing a breaking pressure for the shear screws. The unlocking sleeve then slides downwards and its lower end 502 pushes the locking sheath 55 back, thus unlocking the dogs 54. The valve in accordance with the invention may be equipped with rigid tubes for supplying injection gas or with flexible tubes, because unlocking takes place in the absence of loads on these tubes. <IMAGE>
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