Rotary shafts – gudgeons – housings – and flexible couplings for ro – Flexible coupling between fluid-conducting rotary shafts – Including member deformable by relative movement between shafts
Reexamination Certificate
2000-02-29
2001-12-25
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Flexible coupling between fluid-conducting rotary shafts
Including member deformable by relative movement between shafts
C464S089000, C464S018000, C175S321000
Reexamination Certificate
active
06332841
ABSTRACT:
DESCRIPTION OF THE INVENTION
1. Technical Field
This invention relates to a cushion sub of a type for absorbing vibrations being transmitted to a drill head by a drill pipe during the drilling of a bore hole.
2. Background Art
It is well known to include a cushion sub below the drill head of a drilling rig and through which the turning force of the drill head is transmitted to the uppermost drill pipe section to thereby rotate the drill string within the bore being drilled. Such cushion subs have taken a number of different forms, the design of which takes into account different features of the drilling operation in association with which the cushion sub will be used. For example, it is common in a drilling operation to force the drilling bit into engagement with the bottom of the bore and to achieve the cutting action due to rotation motion only of the bit. A cushion sub designed for this type of drilling must be capable of absorbing a significant portion of both the torsional and axially vibrations developed by the cutting action of the bit, but most importantly, it must be designed to accommodate high torsional forces. In the use of downhole hammer drilling, drilling is achieved by additional axial vibrating of the drill bit usually by way of a compressed fluid transmitted to a hammer means at the bit location. While the cushion sub used in the past for this type of drilling had to be capable of transmitting a drilling torque as well, the cushion sub was primarily designed to prevent the transmission of high axial vibration forces to the drilling head. Thus, it did not need the same type of means to prevent the transmission of large torsional vibration forces as in the previously described cushion sub. In this regard one might compare the two different type of structures of applicant's U.S. Pat. No. 5,224,898, Johnson, and U.S. Pat. No. 4,759,732, Jul. 26, 1988, Johnson.
More recently, however, different practices of drilling have developed. For example, in the drilling of pile holes for construction and in the drilling of blast holes used in mining, downhole hammering has been used for drilling holes of much larger diameter than previously made. In an attempt to cope with the higher torsion vibrations developed under these conditions, cushion connectors of the type shown in U.S. Pat. No. 5,224,898 have been utilized. This has not proven completely satisfactory, however, in that the resilient means used in the connector of this patent has not been designed for the transmission of the axial forces present in the downhole hammer type drilling.
DISCLOSURE OF INVENTION
Accordingly, it is an object of the present invention to provide a cushion sub having both axial and torsional vibration absorbing characteristics capable of effectively handling the types of forces being experienced in modern drilling techniques.
The cushion sub of the present invention, which is used for connection between a driving member and a driven member in a drill string to effectively absorb both torsional and axial vibrations in the drill string, is of the type including a main body having an outer casing member. The casing member includes a first end cap which is provided with a first connection means at one end of the main body for rigid connection to one of the driving and driven members of the drill string, usually the driving member. A cylinder member is disposed within the outer casing member and defines an inner cylinder chamber, and a piston member is disposed within the cylinder chamber for axial movement between extreme inward and outward positions. A piston shaft extends from the piston member through the other end of the casing member. The piston shaft has second connection means at a free end thereof for rigid connection to the other of the driving and driven members of the drill string, usually the driven member. The cylinder member has internal spline means cooperating with external spline means on the piston member for preventing relative rotation between the piston member and the cylinder member while permitting the axial movement of the piston member relative to the cylinder member between the inward and outward positions. Cushion means is provided at opposite ends of the cylinder chamber for engagement by the piston in either of the extreme positions for absorbing axial vibrating and preventing transmission thereof between the piston member and the cylinder member.
According to one aspect of the present invention, the cylindrical member has an outer surface disposed radially inward from an inner surface of the casing member so as to form an annular space therebetween. First circumferentially spaced vane members project radially outward from and are integrally formed with the outer surface of the cylinder member, the vane members extending axially along the outer surface within the annular space. Second radially inward projecting vane members are integrally formed with the inner surface of the casing member, the second vane members being circumferentially spaced from each other and being disposed between and circumferentially spaced form the first vane members. Resilient cushion means is disposed in the annular space between and separates the first and second vane members, so as to absorb torsional vibrations and thereby prevent transmission of torsional vibrations between the cylinder member and the casing member.
According to another aspect of the present invention, the casing member has a cylindrical inner surface defining a closed chamber, and a plurality of first, circumferentially spaced, vane members project radially inward from the inner surface of the casing member. A plurality of second, circumferentially spaced vane members are affixed to the cylinder member and project radially outward between, but circumferentially spaced between the first vane members in the closed chamber. A resilient cushion medium occupies the closed chamber and separates the first and second vane members. The cushion medium formed in situ in said closed chamber by injecting said medium in a fluid state into said closed chamber is thereby bonded to said first and second vane members so that the cushion medium effectively absorbs torsional vibrations being transmitted between the cylinder member and the outer casing.
REFERENCES:
patent: 3779040 (1973-12-01), Garrett
patent: 4055338 (1977-10-01), Dyer
patent: 4109488 (1978-08-01), Work
patent: 4192155 (1980-03-01), Gray
patent: 4571215 (1986-02-01), Hansen
patent: 4759738 (1988-07-01), Johnson
patent: 5224898 (1993-07-01), Johnson et al.
patent: 5476421 (1995-12-01), Moore et al.
patent: 5588916 (1996-12-01), Moore
patent: 12 19 855 (1987-03-01), None
Browne Lynne H.
Dunwoody Aaron
Foremost Industries Inc.
Kerins John C.
Miles & Stockbridge P.C.
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