Patent GB-781859-A (GB)
Title: Improvements in or relating to well-drilling units
Inventor: WHITTLE FRANK
IPC: E21B4/00
Filed: 1954-06-22
Abstract: 781,859. Stuffing-box substitutes. NAAMLOOZE VENNOOTSCHAP DE BATAAFSCHE PETROLEUM MAATSCHAPPIJ. Sept. 23, 1954 [June 22, 1954], No. 18286/54. Class 122 (5). Pressure balancing means, for a sealing assembly used to seal a cavity 1, Fig. 1, in the sub-surface part of a well-drilling unit comprising a drill bit directly coupled to and driven by a submerged hydraulic turbine or electric motor, is constituted by at least one membrane or flexible diaphragm 13, one side of which is exposed to the hydrostatic pressure outside the cavity 1 while the other side is in contact with the liquid in the cavity. As shown, the cavity 1 is surrounded by a member 2 mounted on a number of wings or ribs 3 in the stator housing 4 of an hydraulic turbine 8, the shaft 7 of which is mounted in a bearing 11. Rubber sealing members 6 close the cavity 1 and hence protect the bearing 11 from the mud flush which flows through the spaces between the ribs 3 to drive the turbine 8. Preferably, a number of flexible diaphragms 13 having the form of a cylindrical bellows is employed, the interior of each bellows being connected to a passage 15 so that variations in the hydrostatic pressure of the mud flush cause the bellows to expand or contract and hence to maintain the pressures inside and outside the cavity 1 substantially equal. In order to prevent the bellows from being affected by the dynamic pressure of the mud flush, the vertical part of the passage 15 is closed at its end by a screw plug 16. Before the unit is lowered into a bore-hole, the cavity 1 is filled with lubricant by means such as grease nipples and care is taken that no vapour or air remains in the cavity after filling has been completed. In a modification of the arrangement shown in Fig. 1, a rubbing-collar type of seal and a single ring-shaped bellows are employed. Fig. 3 shows a sealing arrangement for a bearing 24 supporting the lower end of the motor shaft which is hollow to receive the mud flush from openings 25 and to guide it to orifices in the drill bit. A rubber seal 28 and a sealing ring 29 loaded by a spring 31 are provided to seal the cavity 1, the volume of which is adjusted by movement of a stepped portion of a bellows 32 to maintain equal pressures inside and outside the cavity 1. To ensure that the pressures on the exterior surfaces of the seals 28 and 29 are substantially equal, passages 36 and two ring members 35 forming a throttle passage are provided. Instead of exposing the cavity 1 to the pressure at the turbine outlet as in Fig. 3, it may be exposed to the lower pressure outside the housing 4 by providing an axial or conical throttle passage 37 or 37<SP>1</SP>, Fig. 4, above the cavity 1, the mud flush leaking through these throttle passages flowing through orifices 38 to the bore-hole. The cavity 1 is sealed by throttle passages 42 and 43 and the pressures inside and outside the cavity 1 are equalized by a flat corrugated membrane 40 and orifices 39. The members forming the throttle passages may be lined with a wear-resisting material, such as rubber or a metal alloy. Two modifications of the arrangement shown in Fig. 3 are described in which a bellows with a reversed step is mounted to project either into the cavity 1 or into the space above the upper seal. Specification 781,860 is referred to.