Joints and connections – Biased catch or latch – By separate spring
Reexamination Certificate
1999-11-22
2001-09-18
Kim, Harry C. (Department: 3629)
Joints and connections
Biased catch or latch
By separate spring
C403S366000, C175S296000
Reexamination Certificate
active
06290424
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a segmented ring mounting for retaining cylindrical components one within the other in a fluid-operated percussion drill tool, such as a downhole rock drill. However, the invention has application to other interengaging cylindrical components which are subject to heavy wear or pressure loading, such as compressors, pumps, borehole tools, casings and drillpipe mountings.
BACKGROUND OF THE INVENTION
Conventional fluid-operated percussion drill tools comprise an external cylinder or outer wear sleeve, within which is mounted an inner cylinder which in turn engages with a backhead assembly. A sliding reciprocating piston cooperates with the inner cylinder and backhead assembly, which when air pressure is supplied through the backhead assembly, acts with a percussive effect on a drill bit retained within a chuck on the outer wear sleeve.
In conventional arrangements, the inner cylinder is effectively suspended within the outer wear sleeve by means of a compressible retaining ring, such as a circlip, which has to be slid up the inner cylinder so as to seat against a shoulder or lip at one end thereof, being compressed when the inner cylinder is dropped down within the outer wear sleeve, and then expanding outwardly into a groove or shoulder formed on the inner diameter of the outer wear sleeve with a snap action. When in this position, the circlip seats within the groove and abuts against the lip of the inner cylinder, by which the inner cylinder is suspended within the outer wear sleeve. Compression of the circlip requires considerable force during this assembly operation.
A disadvantage with the circlip mounting system is that the inner cylinder may move during operation because of vibration, and the lip may become deformed, and unevenly worn due to wear between the lip and the circlip. The circlip is not a complete ring and includes a gap, and there is therefore no wear on the lip above the circlip gap. The hardness of the steel from which the inner cylinder and the circlip are made may not be the same, which also contributes to wear between these two components.
However, if the inner cylinder is removed from the outer wear sleeve for maintenance or inspection purposes, and then reassembled in the manner described above, the circlip is most likely to snap into place in the groove in the outer wear sleeve in a different position, i.e. the circlip gap is likely to be in a different position, so that wear between the circlip and the lip of the inner cylinder will be concentrated on a different portion of the lip. With continued wear, the result is that a slightly raised portion of the lip or lump will develop, and the presence of one or more lumps around the circumference of the lip caused by this uneven wear will result in poorer engagement between the inner cylinder and the outer wear sleeve, and even a skew or off-center between the two cylindrical components, which will rapidly increase wear between the components and shorten the life of the downhole drill.
The present invention seeks to provide a solution to the general problem of awkwardness and difficulty of assembly and reassembly of parts using a conventional circlip mounting, and furthermore to address the problems caused by uneven wear between the conventional circlip and the lip of the inner cylinder.
SUMMARY OF THE INVENTION
According to the present invention there is provided a retaining ring for seating a smaller diameter cylindrical component within a larger diameter cylindrical component, wherein one of the components is formed with a groove or shoulder for seating the retaining ring in use, the ring being capable of radial compression and expansion so as to expand radially into the seating groove or shoulder for retaining the components one within the other in use, characterized in that the retaining ring comprises at least three segments, which when touching end to end form a complete circle, and expansible holding means biassed to hold the segments together but of sufficient elasticity to allow the segments to expand radially and move apart by a sufficient amount so as to seat the segments in the groove or against the shoulder.
Preferably, the segments are formed with an outer groove, and the holding means comprises an O-ring placed in the outer groove.
Advantageously, the smaller diameter cylindrical component includes a lip for engagement with the retaining ring, and an inclined surface defined between the lip and an outer diameter of the said smaller diameter cylindrical component, which inclined surface causes the segmented retaining ring of the present invention to slide into abutting engagement with the lip and causes it to expand into the seating groove or against the shoulder, when the smaller diameter cylindrical component is dropped inside the larger diameter cylindrical component during assembly of the two cylindrical components.
REFERENCES:
patent: 2855003 (1958-10-01), Thaxton
patent: 3797336 (1974-03-01), Howe
patent: 4598916 (1986-07-01), McGehee
patent: 4630958 (1986-12-01), McCallister
patent: 5005877 (1991-04-01), Hayman
patent: 5209521 (1993-05-01), Osborne
patent: 5542481 (1996-08-01), Scott
patent: 5685380 (1997-11-01), Purcell et al.
patent: 0798815 (1997-10-01), None
patent: 2296731 (1996-07-01), None
Examiner Bellingacci, F., European Search Report for Application No. EP 99203902, Mar. 21, 2001, pp. 1-3.
Cahill Sutton & Thomas P.L.C.
Kim Harry C.
Minroc Technical Promotions Ltd.
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