Title:
Shrouded drill bit
United States Patent 2261546


Abstract:
This invention relates to drill bits of the type having a plurality of roller cutters for drilling hard formations in deep wells, and is particularly directed to an arrangement of a shroud or enclosure for said cutters which will provide an opening through which the cutters may extend to be...



Inventors:
Gipson, Willard W.
Application Number:
US30820039A
Publication Date:
11/04/1941
Filing Date:
12/08/1939
Assignee:
Gipson, Willard W.
Primary Class:
Other Classes:
175/313, 175/340, 175/375
International Classes:
E21B10/08
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Description:

This invention relates to drill bits of the type having a plurality of roller cutters for drilling hard formations in deep wells, and is particularly directed to an arrangement of a shroud or enclosure for said cutters which will provide an opening through which the cutters may extend to be operative, but which will prevent their loss if the cutter support means should fail.

Heretofore roller cutter bits have been provided with shrouds which are adapted to extend only over the upper portion of the rollers to direct downwardly the stream of driiling mud fluid which is used to wash the cuttings out of the bore hole and also to cool and lubricate the bit itself. Such shrouds are illustrated in Patents Nos. 1,236,983 and 1,263,802 to Reed; 1,289,179 to Hughes; and 1,736,840 to Scott.

This invention is an improvement over the structures illustrated in those patents and comprehends broadly a shroud which extends downwardly and also inwardly around the rotating cutters so as to permit them to act on the material to be drilled but will retain them if the pin or spindle on which they rotate should become fractured. The loss of such cutters in very deep bore holes is quite frequent and necessitates the removal of the long drill pipe and the insertion of some sort of fishing tool to remove the broken parts. If these parts are not removed they interfere seriously with a new drill bit and may damage it severely before being pushed aside in the formation or reduced to small pieces by the action of the new bit.

A second feature of this improvement is in the provision of a strong and substantial shroud, the bottom of which is spaced .a predetermined distance above the lowest point on the teeth of the roller cutters so that when the latter are worn to a predetermined degree the bit will skid around on the formation and indicate to the driller that the cutters are no longer in effective condition for further drilling. This prevents long continued rotation of ineffective bits.

These and other objects of the invention will be more fully apparent from the following description and from the appended drawing, which forms a part of the specification and illustrates a preferred form of the invention, In the drawing, Figure 1 represents a bottom view of a drill bit employing frusto-conical rotary cutters and fitted with a shroud embodying the invention, Figure 2 is a side elevational view of the bit of Figure 1 and illustrates one method of securing the shroud to the body of the drill bit.

Referring to Figure 2, the bit is illustrated as having a body 10 which is adapted to be secured to the lower end of a conventional string of drill pipe by means of a threaded portion I . The body 10 is provided with downwardly extending supports 12 for a plurality of frusto-conical toothed cutters 13 which may be secured In any desired manner. The shrouds 14 which form a principal part of this invention are substantially L-shaped with a shank which conforms to the particular bit and is secured to body 10 and members 12 by any suitable means such as a welded seam 15. The outer faces of the shank portions of shrouds 14 may be recessed as at 16 to provide adequate passage for mud fluid and ,cuttings upwardly around the bit. The lower portion of each shroud 14 is generally at. right angles to the shank and usually extends inwardly toward the center of bit 10.

The lower faces 17 of shrouds 14 are extended transversely toward the cutter axes as indicated in Figure 1 and may be notched or recessed, if desired, so as to enclose enough of the cutters 13 which, in this example are frusto-conical, but which can be of any desired configuration or arrangement, so that the latter will be retained if their support pin or spindle should become broken. The lower face II of shrouds 14 also serves an added purpose of being spaced a predetermined distance "A" above the lowest point on the teeth of rollers 13 so that when the teeth are worn to a degree which will permit the bit to slide or skid on surface 17 the driller will be able to tell by the behavior of the drilling apparatus that the bit has been worn so as to be inefficient. Distance "A," therefore, will be somewhat less than the length of the longest teeth. In this way he will be able to replace such bits with a minimum of lost time from actual drilling operation.

Although a specific embodiment of this invention has been described and illustrated, it is to be understood that variations in its arrangement, and particularly in the configuration of the shrouds and their manner of attachment to the body of the bit, may be made without departing from the invention, and all such modifications and changes as come within the scope of the appended claims are embraced thereby.

I claim: 1. A shroud for a drill bit haying spaced rotatable toothed cutters, said shroud comprising a generally L-shaped member having a shank portion shaped to conform to the body of said bit between adjacent cutters, and another portion at substantially right angles to said shank adapted 50. to overlap a portion of at least one of said cutters below its axis and still permit its working teeth to extend beyond the outer face of said shroud.

2. A shroud for a drill bit having spaced rotatable toothed cutters, said shroud comprising a generally L-shaped member having a shank portion shaped to conform to the body of said bit and another portion at substantially right angles to said shank and notched to extend beneath at least a portion of one of said toothed cutters below its axis of rotation.

. WILLARD W. GIPSON.