PIG Russian patent published in 2015 - IPC E21B43/18 E21B43/25 

FIELD: machine building.

SUBSTANCE: pig has casing with central internal channel, through top and bottom side holes and check valve. This valve is equipped with central top stock, internal spring-loaded safety valve and through vertical holes in top end wall. Casing contains two coaxial bushings, top and bottom, and support section installed on the stock with possibility of rotation. At acute inclination angle to the central axis of the casing a between bushings ring clearance is made. Its peripheral edges are located on side surfaces of bushings. Top bushing is made with through inclined holes. They are connected with the clearance with possibility of creation of the hydraulic seal between the pig casing and pipe string during the pig movement. Bottom bushing is made with through side holes in top part. Facets of the ring clearance, top base of top bushing, cylindrical surface of each inclined hole of the top bushing are made interfaced. Besides, check valve installed in the support section with possibility of vertical movement is equipped by side contracting nozzles. They coincide with side through windows of the support section.

EFFECT: increased reliability of work and extension of process abilities of the pig.

2 cl, 3 dwg