| 摘要 |
A ball dropping assembly for dropping an object such as a spherical ball into a wellbore. The assembly comprises a seat for retaining a ball before it is released, a ball retaining lever, and a shaft for turning the lever. In one embodiment, the assembly is attached to a side bore in fluid communication with a main bore in a cementing head. The ball-retaining lever has at least one finger which is rotated between a ball-retained position and a ball-released position. In the ball-retained position, the first finger is disposed in the entrance from the side bore to the main bore, thereby preventing the ball from entering the main bore of the cementing head. When the ball is ready for release, the lever is rotated in the direction of the main bore, thereby causing the second finger to urge the ball into the bore of the cementing head, and causing the first finger to protrude into the main bore. When a plug is released into the bore from the cementing head, the plug will trip the first finger, causing the ball-retaining lever to rotate back towards the ball-retained position. Thus, the ball dropping assembly also serves as a plug release indicator.
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