US3490551A - Valve-type percussion drill bit - Google Patents

Description

Jan. 20, 1970 P. G. GATIE'N 3,490,551

VALVE-TYPE PERCUSSION DRILL BIT Filed D80. 27. 1967 4a /4 J Y 4 'J/ 4 f i l i V g5 55 i Z I (k 2a 17/ 2 22 INVENTOR TAM. 6,. @HT/EA/ ATTORNEYS.

United States Patent Int. Cl. B21b 1/00 U.S. Cl. 175-318 4 Claims ABSTRACT OF THE DISCLOSURE By this invention an improved valve is provided for a valve type percussion drill bit. The valve includes a structurally rigid cylindrical peripheral portion, made substantially entirely out of rubber or including a facing of rubber reinforced fabric. The cylindrical height (h) is predetermined. An integral central disc portion is provided whose top surface is flush with the top surface of the cylindrical portion. The thickness (1) of the disc is also predetermined. The disc is provided with at least two and preferably four slits originating at the geometric center of the disc and extending radially less than the radius of the disc, to provide at least two and preferably four normally closed valve flaps. A critical relationship has been discovered between (h) and (t), nam ly, (1) ranges for /2 (h) to A (h).

This application is a continuation-in-part of application Ser. No. 647,879 filed June 21, 1967, which is a continuation of application Ser. No. 405,672 filed Oct. 22, 1964 (now abandoned). Application Ser. No. 647,879 was issued Feb. 27, 1968, as Patent 3,370,659.

The present invention relates to an improvement in the so-called valve type percussion drill bits, and particularly to a novel valving arrangement for such drill bit.

It is well known that bore holes may be formed in the substrata by positioning a drill bit on the end of a drill rod and then rotating the drill rod and bit while applying a percussive pressure against the other end of the drill rod. The drill bit is usually attached to the drill rod by a screw thread arrangement. The drill rod is hollow and the drill bit is provided with apertures or holes in communication with the hollow drill rod to allow drilling fluid or are to be forced down the drill rod through the drill bit and into the bore hole for purposes of cleaning the bore hole by forcing drilling residue material up between the outer sides of the drill rod and the walls of the bore hole to the surface. This is standard practice in the art and it is known that it is necessary to force drilling fluid or air down the bore hole under high pressure to accomplish cleaning of the bore hole. This is especially true of very deep holes.

It is also known that the life of the sharpness of a drill bit is relatively short and that it is necessary to remove all of the drill pipe from the hole to change the drill bit at frequent intervals. Before the drill rod is withdrawn from the hole, the supply of drilling fluid or air pumped down the drill rod is discontinued. With this release of pressure there is a tendency for the drilling fluid remaining in the bore hole to reverse back into the drill rod carrying with it the gritty rock slush resulting from the drilling operation. The drilling fluid and grit is forced back into the drill rod through the drill bit and up into the threads joining the drill bit to the rod.

When the terminal end of the drill rod carrying the drill bit is brought to the surface it has been found that the impregnation of the gritty drilling mud into the screw threads joining the drill bit to the drill rod makes it 3,490,551 Patented Jan. 20, 1970 very diflicult to remove the bit and once removed it is found that the threads on the bit are so worn and out as to render the bit useless for further service.

In copending application Ser. No. 647,879 filed June 21, 1967 applicant has provided a valving arrangement such that the drilling fluid under pressure may pass d wn the rod into the bit and into the bore hole, but which automatically prevents gritty and dirty drilling fluid from passing from the drill bit back into the drill rod when the application of percussive pressure downwardly in the drill rod and the application of drilling fluid under pressure in the drill rod is stopped. The valve disclosed therein was of a particular construction which enabled it to operate effectively even when the drill rod and bit were vibrated because of the application of percussive pressure.

The particular structure of the one way valve disclosed and claimed in the aforementioned application Ser. No. 647,879 which enables it to operate effectively under the adverse drilling conditions discussed above is embodied in the following essential integers, namely: the valve must be formed of resiliently deformable material and must be of generally ring shaped con-figuration and including a peripheral portion adapted to be clamped between the drill rod and the drill bit. The valve includes a central depressed portion, usually conical, with a plurality of slits originating at the vertex of the depressed portion and extending radially outwardly less than the radius of the central depressed portion. The valve is mounted so that the central depressed portion is directed towards the apertures of the drill bit.

While this valve has made possible the use of a drill rod and drill bit combination for percussive and rotary drilling, occasionally, particularly when the diameter of the drill rod is greater than about six inches, some failure in the valve has been noted. Thus, under these circumstances, some leakage of the gritty and dirty drilling fluid into the drill rod has taken place.

Accordingly, it is an object of a broad aspect of this invention to provide an improvement in the aforedescribed valve for a valve-type percussive drill bit.

An object of another aspect of this invention is the provision of an improved valve for a valve-type percussive drill bit particularly adapted for use with drill bits of diameter greater than about six inches.

It has now been found that an improved such valve is provided by a resilient member having a structurally rigid cylindrical peripheral portion and an integral disc portion coextensive with the flat face of the cylindrical portion, the central disc being thinner than the height of the cylindrical peripheral portion. There is a critical relationship between the thickness of the disc I and the height of the cylindrical peripheral portion h. Thus, it has been found that h=from 4! to 2t. The central disc is also provided with at least two slits, originating at the center and extending radially outwardly less than onehalf the diameter of the central disc.

Thus, by one broad aspect of this invention, a drill bit assembly is provided which is adapted to be detachably secured to a drill rod provided with a central bore, the drill bit assembly comprising: (A) a drill bit including, (1) a central bore provided with internal threads for threaded engagement with external threads of a drill rod; (2) a central well concentric with said bore but of lesser diameter thereof; (3) a plurality of apertures extending generally outwardly from the central well; (4) a plurality of drilling flanges disposed around the outer circumference thereof; and (5) a cylindrical valve seat, concentric with the central well, of lesser diameter than the drill bit bore, but of greater diameter than the central well; and (B) a valve element disposed in the valve seat, the valve element comprising a resilient member having: (i) a structurally rigid cylindrical peripheral portion, adapted to be clamped between the drill rod and the drill bit to prevent relative movement of the valve ,element; and (ii) an integral central disc portion coextensive with the flat face of the cylindrical portion which is facing the central bore, the central disc portion being of predetermined thickness, the disc portion being provided with at least two slits originating at the center thereof and extending radially less than one-half the diameter of the central disc to provide at least two normally closed flaps, the predetermined thickness of the central disc being between one-quarter and one-half the height of the cylindrical peripheral portion, whereby fluid passing through a drill rod in the direction of the drill bit urges the valve flaps open so that fluid may pass through the valve element, and whereby fluid under pressure attempting to pass through the drill bit to the drill rod will urge the valve flaps to a closed position to prevent fluid from passing therethrough.

In the accompanying drawings,

FIGURE 1 is a cross-sectional view of a drill rod and attached drill bit and a valve according to an aspect of the present invention in closed position in position therein;

FIGURE 2 is a cross-sectional view of a drill rod and attached drill bit and a valve according to an aspect of the present invention in open position in position therein;

FIGURE 3 is a section taken along line 3-3 of FIG- URE 1;

FIGURE 4 is a section taken along line 4-4 of FIG- UR E2; and

FIGURE 5 is a perspective view, partly broken away, of the valve of an aspect of this invention.

As seen from FIGURE 1-4, the valve of one aspect of this invention is disposed between a drill bit 11 and a drill rod 12. The drill rod 12 is provided with a central bore 13 and a plurality of terminal external threads 14. The terminal face 15 of the drill rod 12 provides a securing surface. The drill bit is provided with a central bore 16 which is tapped at 17 to provide engagement of threads 14 with tapping 17 for securing the drill bit 12 to the drill rod 11. The central bore 16 terminates in a central cavity 18 of less diameter than central bore 16, the bottom surface of the central cavity 18 providing a valve seat 19. Central cavity 18 leads to a central well 20 from which are a plurality of generally downwardly extending apertures 21. The drill bit 11 is also provided with a plurality of external drilling flanges 22.

Drilling fluid or air under pressure is forced in the direction of arrow 23 down through the drill rod bore 13 and thence through apertures 10 into a bore hole (not shown) to force drilling residue to the surface. The valve 10 is retained in its operative position on the valve seat 19 by means of engagement between terminal face 15 and the upper face 25 of the valve 10. The lower face 26 rests on valve seat 19.

As above explained, it has been found that when the application of pressure against the drilling fluid in drill rod 12 ceases, the back pressure of the drilling mud and grit in the bore hole forces'the drilling mud back up into the drill rod 12 in the direction of arrow 24 in FIG- URE 2 and into the threads 14 of the drill bit 11 and drill rod 12.

The simple and inexpensive valve arrangement shown generally by numeral 10 in cross-section in FIGURES 1 and 3 and in partial top view in FIGURES 2 and 4 is now provided to minimize or substantially eliminate this baclcflow of drilling mud and grit.

It is seen that the valve 10 comprises a peripheral structurally rigid peripheral portion 30 which may be formed of a suitable rubbery material alone, as shown in FIG- URES 14, or it may be provided with a circumferential face 31 formed of fabric reinforced rubber, as shown in FIGURE 5. The cylindrical peripheral portion 30 is adapted to be clamped between the drill rod 12 and the drill bit 11, with one face 26 resting on valve seat 19, and face 25 engaging face 15. A central disc portion 32 is provided which is integral with the peripheral portion 30 and whose top face is coextensive with top face 25. Disc 32 is of a thickness t which is correlated to the height h of peripheral portion in the following manner:

= /2 to %h One suitable interrelation exists when h= /2" and t=%".

As shown in FIGURE 3, the disc portion 32 is provided with four slots 33, 34, 35 and 36, providing four flaps 37, 38, 39, 40. Each slot originates at the geometric center of the disc 32 and extends radially outwardly for a distance less than the radius of the disc 32. As seen more clearly in FIGURE 4, the downward opening movement of flaps 37, 38, 39, 40 causes an access aperture 41 to be formed in the central portion of the disc 32.

FIGURE 5 shows another embodiment of this invention in which two slots 42 and 43 extend through the thickness t of the disc 32, the slots extending from the geometric center radially outwardly by an amount less than the radius of the disc 32. This provides two valve flaps 44, 45.

The valve 10 is mounted in the drilling assembly comprising the drill rod 12 and the drill bit 11 with the top surface of the disc 32 flush with the top portion 25 of the peripheral portion 30.

The valve 10 is constructed of any suitable resilient material such as hard rubber, resilient plastic or like material and, as stated hereinbefore, is mounted within the drilling head between valve seat 19 provided in the drill bit 11 and the end 15 of drill rod 12. The valve 10 is so constructed that the slits 33, 34, 35, 36 in the disc portion 32 are normally in closed position, as shown in FIGURES 1 and 3.

When drilling fluid or air under pressure is forced down the drill rod 12 in the direction of arrow 23, the valve flaps 37, 38, 39, 40 bounding the slits 33, 34, 35 and 36 will be forced open, due to the pressure on the slits and the configuration of the valve 10, to the position shown in FIGURES 2 and 4. The drilling fluid can then continue through the apertures 21 in the drill bit 11 and into a bore hole (not shown).

When the downward pressure on the drilling fluid or air in drill rod 12 is stopped, and the back pressure of the fluid in the bore hole reverses back through apertures 21, the flaps 37, 38, 39, 40 close due both to their nature of construction and to the upward pressure against them. This closing effectively prevents gritty drilling fluid or air from passing upwardly into the drill rod 12 and into the thread arrangement 14, 16.

The valve of aspects of this invention is simple and economical and can easily be constructed for adaptation to all types of drill rod and bit assemblies. Furthermore, although it is particularly adapted for use in drill bit assemblies of internal diameter six inches or more, it is equally useful in drill bit assemblies of lesser internal diameter.

I claim:

1. A drill bit assembly adapted to be detachably secured to a drill rod provided with a central bore, said drill bit assembly comprising:

(A) a drill bit having:

(1) a central bore provided with internal threads for threaded engagement with external threads of a drill rod;

(2) a central well concentric with said lbore but of lesser diameter thereof;

(3) a plurality of apertures extending generally downwardly from the central well;

(4) a plurality of drilling flanges disposed around the outer circumference thereof; and

(5) a cylindrical valve seat, concentric with said central well, of lesser diameter than said drill bit central bore, but of greater diameter than said central well; and a (B) a valve element disposed in said valve seat, said valve element comprising a resilient member having: (i) a structurally rigid cylindrical peripheral portion of a predetermined height (h) and adapted to be clamped between the drill rod and the drill bit to prevent relative movement of the valve element; and (ii) an integral central disc portion coextensive with the flat face of said cylindrical portion which is facing said drill bit central bore, said central disc portion being of predetermined thickness (t), the disc portion being provided with at least two slits originating at the center thereof and extending radially less than one-half the diameter of said central disc to provide at least two normally closed flaps, wherein (t) varies from /2 (h) to A (h). whereby fluid passing through the drill rod in the direction of the drill bit urges the valve flaps open so that fluid may pass through the valve element, and whereby fluid under pressure attempting to pass through the drill bit to the drill rod will urge the valve flaps to a closed position to prevent fluid from passing therethrough.

References Cited UNITED STATES PATENTS 571,708 11/1896 Thompson 137525.1 2,335,832 11/1943 Williams 137-525.1 X 2,724,442 11/ 1955 Mundt 166--225 3,007,527 11/ 1961 Nelson 166-225 3,089,551 5/ 1963 Greene 175-318 3,268,018 8/ 1966 Neilson 175340 X CHARLES E. OCONNELL, Primary Examiner IAN A. CALVERT, Assistant Examiner US. Cl. X.R.

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