Rotary expansible chamber devices – Unlike helical surfaces on relatively wobbling rotating...
Patent
1991-08-08
1993-06-22
Vrablik, John J.
Rotary expansible chamber devices
Unlike helical surfaces on relatively wobbling rotating...
418178, 29888023, F01C 1107
Patent
active
052211975
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to drilling equipment and, more particularly, to a working member of downhole motors for drilling oil and gas wells. The working member of a helical downhole motor can be either a rotor or a stator having helical teeth operating in conjunction, and normally is known as a working pair of the motor.
PRIOR ART
There is known a working member of a helical downhole motor in the form of a rotor, or a stator with the rotor having one or more teeth, and the stator having two or more teeth. In each working pair, the numbers of teeth in the stator and rotor differ by one.
As a rule, the know downhole motors have metal one-piece rotors of solid or tubular construction. The stators are normally rubber-metal with inner helical teeth on an elastomeric lining connected by vulcanization with a cylindrical bore of the metal body of the stator. The number of pitches of helical teeth in a working pair of the known motors is generally somewhat more than two. Provision of a greater number of pitches of helical teeth in the working pair is associated with technical difficulties. However, an increase in the number of pitches is necessitated by an increase in the moment of force at the output shaft influencing the drilling performance. There is a trend to increase the number of pitches in the working pair through providing a working member made up of separate interconnected sections.
There is known a multipitch working member of a helical downhole motor in the form of a rotor or a stator (cf., U.S. Pat. No. 3,912,426). The rotor includes separate sections with outer helical teeth arranged in succession, one after another, and rigidly interconnected by welding. The stator also includes separate sections with inner helical teeth, and a means for joining the sections. This means has the form of holes at one end of the adjacent sections and pins at the other end. End sections of the stator are clamped in the casing by a threaded connection.
However, this construction of the means for joining the sections of the working member necessitates very accurate orientation of the working helical surfaces of the rotor whose sections are interconnected by welding, and also necessitates mechanical working of the welded seam between the sections, which is especially difficult for multiple rotors having a number of teeth greater than one, and intricate cross section. When using a stator as the working member, reliability of the joint between the sections is affected, because the moment of force is transmitted between the sections through the pins of relatively small diameter determined by the cross section of the motor and height of the stator tooth. This disadvantage is especially pronounced in multilobe stators characterized by a high moment of force.
French patent No. 2,349,729 teaches a working member of a helical downhole motor for drilling wells, such as a rotor, made up of separate sections with outer helical teeth arranged in succession one after another, and joined by a connecting means. This means for joining the sections includes a rod element onto which the rotor sections are successively mounted. End faces of the rotor sections have holes to receive pins connecting the sections. Several rotor sections arranged in succession on the rod are secured at the ends by a threaded connection. The rotor of this construction accommodates, at the rod, rotor sections of different lengths which are easy to manufacture. The length of each such section can vary from 15 to 30 cm.
The working member of this helical downhole motor acting as a stator or as a rotor includes separate sections arranged in succession one after another. The ends of the stator sections have holes receiving pins to join the sections, whereas the ends of the stator sections are secured in a casing by means of a threaded connection.
However, in this working member of a helical downhole motor, the sections are not sufficiently reliably interconnected, as the moment of force is transmitted between the sections of the working memb
REFERENCES:
patent: 3499389 (1970-03-01), Seeberger et al.
patent: 3912426 (1975-10-01), Tschirky
patent: 4140444 (1979-02-01), Allen
patent: 4415316 (1983-11-01), Jurgens
Goldobin Vladimir B.
Kochnev Anatoly M.
Vshivkov Andrei N.
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