US2657909A - Wear indicator - Google Patents

Description

NOV. 3, 1953 w, BIELSTEm 2,657,909

WEAR INDICATOR Filed March 11, 1949 ATTORNEY.

Patented Nov. 3, 1953 WEAR INDICATOR Walter J. Bielstein, Houston, Tex., assignor, by mesne assignments, to Standard Oil Development Company, Elizabeth, N. J a corporation of Delaware Application March 11, 1949, Serial No. 80,834

3 Claims.

This invention relates to a drill bit used for drilling boreholes into subsurface formations. More particularly, this invention relates to a drill bit which, when it is worn by a pre-determined amount during drilling operations, will give a signal of such wear at the surface of the earth.

In the drilling of boreholes into subsurface formations by the rotary drilling method, particularly in drilling boreholes for the production of minerals, such as oil and gas, the drill bit attached to the end of the drill stem is subjected to conditions which cause rapid wear of the cutting edges of the bit blades. The blades of several bits are ordinarily worn off in drilling such a well. Of course, when the blades are worn off a particular bit, the drilling crew must pull the drill stem out of the hole and replace the worn bit with a new bit before resuming drilling operations. When conventional bits are employed in such operations, no positive method is available for determining the point when the cutting blades of the drill bit are worn to such an extent as to require replacement of the bit; consequently, the selection of the time when the drill bit should be removed from the hole is wholly within the judgment of the drilling crew. As would be expected, conventional drill bits are sometimes removed from the hole before the blades have been worn to the point where the drill bit should really be replaced. On the other hand, and perhaps more commonly, the drill stem is sometimes not withdrawn from the hole and the bit replaced until long after the blades have been worn to such an extent that little or no hole is being made. As a matter of fact, drilling is sometimes continued until the bit blades have been completely worn off the bit body and the bit body itself damaged by wear.

Although excessive wear of the cutting edge of the bit blades is the most frequent reason for replacement of conventional drill bits, it sometimes happens that the bit should be replaced because it has become worn out of gauge. Here again the drilling crew has no positive means of knowing when the bit has become so worn. A drill bit is said to be worn out of gauge when the reaming edges of the bit blades have been worn to such an extent that the diameter of the hole being made is smaller than may conveniently be tolerated. For example, the diameter of a hole drilled with a bit having worn reaming edges may not be sufliciently great to permit the free passage of a new unworn drill bit subsequently introduced into the hole. When this condition exists, the bore-hole walls must be enlarged by reaming in a suitable manner as with a new bit. Not only does reaming consume time but it also entails the risk of a stuck drill bit.

It is an object of this invention to provide a drill bit which, when worn by a pre-determined amount, will cause a decrease in fluid pressure in the mud stream used with the drill string and thus give a signal to the drilling crew indicating that the drill bit should be removed because of excessive Wear.

It is a further object to provide a drill bit, the body of which will not be damaged during drilling operations and in which the construction is such that repair of the used bit is convenient and simple.

The foregoing objects, as well as other advantages, are attained by the present invention as will be apparent from the following detailed description taken in connection with the accompanying drawing in which Fig. 1 is a front view, partly in cross-section, of a drill bit constructed in accordance with the present invention; and

Fig. 2 is a side view of the embodiment shown in Fig. 1.

Referring to the drawing in which like numorals refer to like elements throughout, the embodiment shown comprises a bit consisting of a body It) and blades II and I2. The body It may be affixed to the lower end of a drill stem l3 by any suitable means, such as by threads, the said drill stem being of conventional design fluidly connectible with a source of drilling fluid under pressure. Body I!) is provided with a hollow internal portion M in fluid communication with drill stem l3 when drill stem [3 is connected with body I9. Ducts l5 and i6, conventionally termed eyes or water courses, fluidly connect the hollow internal portion M of body Ill with the outer surface of said body, the outer terminus of ducts l5 and I5 being above the upper edge of bit blades I I and I2, respectively, and normally directed in front of the cutting faces I! and I8, respectively, of the said blades. Bit blades II and I2 may be of any desired design and preferably are made of hard, tough, metallic materials. The reaming edges l9 and 2t of bit blades II and I2, respectively, are approximately parallel to each other and to the longitudinal axis of body I 0. Cutting edges 2! and 22 of bit blades II and 12, respectively, may be perpendicular to the axis of body I0 though they may taper outwardly and downwardly as shown in the drawing. The cutting face I! of bit blade II is disposed approximately from the cutting face [8 of 3 bit blade l2. Bit blades II and I2 may be incorporated into the lower end of body ID in any suitable manner and are normally afllxed to the said body by welding. The drawing shows a dual-bladed bit for the sake of simplicity although it will be understood that the bit of my invention may have a greater number of blades.

The structure heretofore described is conventional to ordinary drag bits. In accordance with the present invention, the aforedescribed structure is modified by providing means for indicating the point at which the bit blades have been worn by a pre-determined amount during drilling operations. Accordingly, body I is provided with duct 23 fluidly connecting hollow internal portion H of said body with the exterior surface of said body above bit blades II and I2. In the drawing, duct 23 is shown as opening into the exterior surface of body It} above bit blade l2 and to the rear of cutting face [8 thereof. Downwardly extending tube 24 is fluidly connected with duct 23 and is anixed to the external surface of body ID. The open lower end 24' of tube 24 is positioned at a point above the lowermost portion of body l0. Plug 25 is adapted to fit slidably into the open lower end 24' of tube 24 and to sealably close said tube. Plug 25 is maintained in sealing-tight relation within lower open end 24' of tube 24 by means of rod 26 which is afilxed, as by tack-welding, at its lower end to a point on the back side of blade l2, its upper end abutting against stopper 25 for holdin the said stopper within the lower open end 24' of tube 24 in fluid-tight relation therewith. The lower end of rod 26 is spot-welded to the back side of blade l2 at the point on blade 12 at which it is desired that wear be indicated. If desired. the upper end of rod 26 may be affixed to plug 25 or rod 26 may be made an integral part of plug 25. The lower end of rod 26 is positioned on blade l2 below the lowermost portion of body ID. The lower end of rod 26 may also be positioned in close proximity to reaming edge 20 of'blade I2, as shown in the drawing.

While plug 25 may consist of any material which will sealably close the lower end of tube 24, I prefer to employ a resilient material such as natural or synthetic rubber. The resilient material may be stiffened, if desired, as by means of integrally included metallic wires or rods.

The structure of my invention having hereinbefore been fully described, its mode of operation will now be briefly indicated. When bit blades H and I2 have been worn during normal drilling operations to the point at which rod 26 is tack-welded to blade l2, the weld on the rod will also be worn off, thereby releasing the lower end of rod 26 from engagement with bit blade l2. With rod 26 removed from its position holding plug 25 in sealing relation within the lower end 24 of tube 24, plug 25 is forced out of the lower open end 24 of tube 24 by reason of the pressure exerted by the drilling fluid with internal hollow portion l4 of body I0 and tube 24. With tube 24 open to the flow of drilling fluid the pressure in drill stern l3 drops and the speed of the mud pump increases, thus indicating to the drilling crew that the bit has become worn to the point at which replacement is required. If the lower end of rod 26 is positioned adjacent the reaming edge 29 of blade 12 as shown in the drawing, excessive wear of the reaming edges I9 and 20 will also eventually wear off the spot-weld at the lower end of rod 26, thus causing a sudden drop in drilling fluid pressure as indicated above.

It is obvious that various changes may be made in the device hereinbefore illustrated and described without departing from the spirit of the invention or the scope of the annexed claims.

What I wish to claim as new and useful and desire to secure by Letters Patent is:

1. A drill bit comprising, in combination a hollow body releasably connectible with a drill stem to a source of drilling fluid under pressure and provided with cutter blades having a cutting face, the body having at least one first duct (or each blade connecting the interior of said body with the exterior of said body above said cutter blade and ahead of the cutting face of said blade, said body having at least one second duct fluidly connecting the interior of said body with the exterior of said body above a cutter blade and to the rear of the cutting face of said blade, a downwardly extending tube in fluid communication at its upper end with the outer terminus of said at least one second duct, the lower portion of said downwardly extending tube being substantially vertically extending, a plug adapted to flt slidably into the lower end of said tube in fluid-tight relation therewith and a rod member mechanically ailixed at its lower end to one of said blades in the path of cutter blade wear and having its upper end abutting against said plug for normal 1y maintaining said plug in fluid-tight relation within the lower end of said tube.

2. A drill bit comprising, in combination, a hollow body releasably connectible with a drill stem to a source of drilling fluid under pressure and provided with cutter blades having a cutting face, the body having at least one first duct for each blade connecting the interior of said body with the exterior of said body above said cutter blade and ahead of the cutting face of said blade. said body having a second duct fluidly connecting the interior of said body with the exterior of said body above a cutter blade and to the rear of the cutting face of said blade, a downwardly extending tube in fluid communication at its upper end with the outer terminus of said second duct and aflixed to the outer surface of said body, the lower portion of said tube being substantially vertically extending, the lower end of said tube terminating above the lowermost portion of said body, a removable plug adapted to fit slidably within the lower end of said tube in fluid-tight relation therewith, a rod member welded at its lower end onto the back side of said blade, the welded lower end of said rod being positioned below the lowermost portion of said body in the path of cutter blade wear, the upper end of said rod member abutting against said removable plug normally to maintain said plug in fluid-tight relation with said tube.

3. A device in accordance with claim 2 in which the removable plug is constructed of rubber.

WALTER J. BIELSTEIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,296,183 Richard Sept. 15, 1942 2,461,164 Lewis a Feb. 8, 1949 2,489,687 Thrift et al. Nov. 29, 1949 2,549,278 Yancey Apr. 17, 1951 2,562,833 True July 31, 1951 FOREIGN PATENTS Number Country Date 295,352 Great Britain Aug. 28, 1928

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