US1952996A - Drill - Google Patents

Description

INVENTOR March 27, 1934. F. K. LANDGRAF I. DMLL Filed Nov. 19. 1981 N i w H Patented Mar, 27, 1934 DRILL Frederick K. Landgraf, Grafton, Pa., asaignor to Flannery Bolt Company, Pittsburgh, Pa., a corporation of Delaware Application November 19, 1931, Serial No. 576,072

4 csims.

The invention relates to multiple-part rock drills of the type in which bits are detachably fastened to drill rods by screw thread connections.

5 As commonly constructed, rock drills of the type herein'contemplated consist of a drill rod ofl a length suitable for the particular hole being drilled, an internally threaded coupling sleeve engaging threads on the outer end of the rod,

and a short detachable bit threaded to be engaged by the coupling. At or near its center the coupling is frequently provided with an inwardly extending shoulder intended to limit the distances the bit and rod can bev screwed into it and at their ends the bit and rod are provided with abuttingprojections of smaller diameter than the bore of the coupling shoulder and intendcd to prevent either the rod or bit from becoming screwed tightly against the shoulder.

In the operation of a drill hammer, the drill rod is normally rotated in a direction tending to tighten its threaded connection to the coupling and that of the coupling to the bit, left hand being customarily used. -If the shoulder and projection construction, just explained, prevents tightening of these connections, there is such 'looseness between the several inter-engaging threads as to permit ingress of the dust or slime of drilled rock, which, on account of the rapid drilling vibrations, quickly abrades the threads particularly when abrasive rock is being drilled. Even in the absence of dust, slime or other abrasive material between the threads, substantial abrasion of the threads may result from the rapid drilling vibrations. This abrasion is not of material consequen'ce as far as concerns the bit and coupling because they are relatively small, cheap and easily renewable members. I'Iowever,I when the threads at the end of a drill 40 rod become abrarled it is necessary to re-thread it because the rod is a relatively expensiv'e member intended for long life and can not economically be discarded merely on account of its threadsbeing abraded. This re-threading involves considerable expense and loss of time because it is necessary to send the rod from the ileld to a machine shop to have its wom thread removed, a new thread put on, and the end of the rod heat treated to give it its required resistance to fatigue. If in the operation of a drill a bit becomes tightly screwed in a coupling, as not infrequently happens regardless of the above-explained instrumentalities intended to prevent it, it is then necessary to apply wrenches or other tools to the bit andcoupling to loosen them, which is timeconsuming and defeats an important advantage of a multiple-part drill, namely, the ready detachability of bits. The importance of this becomes apparent when consideration is given to the fact that ordinarily a bit does not drill very to many minutes in hard rock before its drilling edges are so worn that it must be replaced.

The objects of this invention are to improve the connections of the parts of multiple-part drills of the character explained, to the .end that the 65 threads on rods will not become rapidly abraded by the operation of drills, and to the further end that bits may be quickly and easily removed and replaced.

The invention is illustrated in the accompanying drawing, of which Fig. 1 is a side view of an assembled drill; Fig. 2 a side view showing the coupling member in longitudinal central section; and Fig. 3 a view corresponding to Fig. 2 with the bit and drill rod detached from the coupling.

The drill provided according to this invention comprises a bit 1, a drill rod 2 and a coupling 3. As far as concerns the form of its cutters, the bit may be of any desired construction. While the coupling may be of various forms, it is prefao erably an interiorly threaded sleeve of the general type illustrated. As far as concerns its general construction, the drillirod may be vof the familiar type provided with a central bore for the passage of compresscd air through it, and through thebit, for the usual purpose.

For connecting coupling 3 to rod 2, these members are provided with cooperating threads formed to prevent relative abrasion-producing movements between the members. For this pur- -l pose these members are prefcrably provided with tapered threads, rod 2 being provided with an extemal tapered thread 5, and coupling 3 'with a cooperating intemal tapered thread 6.' While various forms of tapered threads may be used, f they are prefcrably of the undulatory and continuously curved type disclosed in Patent No. 1,642,183 to F. W. Thurston with the attending advantages .dscribed in that patent. By providing the end of the drill rod and the end of the coupling attached to 'it with cooperating tapered threads, the operation of the drill hammer screws these members soitightly together that there is no loose play between them and little, if any, possibility of abrasive material get- 1 ting between them. Consequently. the threads of the rod do not become abraded, even though some rock dust may be lodged between these parts when they are screwed together.

For connecting bit 1 to couqlina 3, these mem- 'the bit to become tightly bers are provided with threads formed to readily permit the bit to be removed from the coupling, and with greater ease than the removal of the coupling from the rod. For this purpose, the shank of the bit is preferably provided with an extemal straight thread 10, and the coupling with cooperating internal straight thread 11, these threads being of greater lead than the co- Operating tapered threads 5 and 6 of the rod and coupling. For ease in the securing of the relatively steep lead of the cooperating bit and coupling threads, a plurality of threads are preferably used, two being shown in the illustrative embodiment of the invention. These threads are also preferably of the undulatory and continuously curved contour disclosed in the above mentioned patent to Thurston.

To prevent a bit from becoming screwed tightly in coupling 3, the end of rod 2 is provided with a projection 15, which, when the coupling is screwed upon the rod as shown in' Fig. 2, extends beyond the inner end of coupling thread 6 to form an abutment for the inner end of the threaded shank of the bit. Accordingly, the bit is continuously held in its relatively loose threaded engagement with the coupling.

In the operation of a multiple-part drill of the type herein disclosed, the customary rotation of a drill rod by a drill hammer tends to continuously tighten the coupling upon the end of the rod, and to screwthe bit into the coupling. The tightening of the coupling upon the end of the rodV is not resisted except by their cooperating tapered threads, and accordingly a tight screw connection is continuously maintained which prevents abrasion-producing relative movements between the rodand coupling. The tendency of screwed in the coupling is resistedw'by the abutting of the end of the shank of the bit"against projection 15 on the drill rod, so that the bit does not become screwed tightly into the coupling and may be readily removed at any time by a few turns of the bit. Furthermore, on account of the greater steepness of the co- Operating threads of the bit and coupling than those of the coupling and rod. the latter become tightened more readily than the former during drilling Operations, which is an additional assurance of desirable tightness between the threads of the coupling and rod, and of desirable looseness between those of the coupling and bit.

lcoupling and bit being A further advantage of the invention attending the provision of a tapered thread on the end of a drill rod is that the rod may be `advantageously thickened at and adjacent to its end to receive the thread and also to increase the resistance of this portion of the rod to breakage, it being understood that the weakest point of the rod is-at or near the threaded end where it is subjected to maximum stresses However, the invention is fully applicable to rods having plain ends.

According to the provisions of the patent statutes, I have explained the principle and operation of my invention, and have illustrated what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A drill comprising a bit, a drill rod,'and a threaded coupling connecting the bit to the rod, the coupling and rod being provided with cooperating tapered threads, and the coupling and bit being provided with cooperating straight threads of greater lead than said tapered threads.

2. A drill comprising a bit, a drill rod, an interiorly threaded coupling sleeve connecting the bit to the rod, the coupling and rod being provided with cooperating tapered threads, and the provided with cooperating straight threads of greater lead than said tapered threads.

3. A drill comprising a bit, a drill rod, and a coupling having separate threads connecting the bit to the rod, the cooperating threads of the coupling and bit being double and of greater lead than those of the coupling and rod to facilitate the removal of the bit from the coupling.

4. A drill comprising a bit, a drill rod, and an interiorly threaded coupling connecting the bit to the rod, the coupling and rod being provided with cooperating tapered threads formed to prevent relative abrasion-producing movements between the coupling and rod during drilling operations, and the coupling and bit being provided with a plurality of cooperating straight threads of greater lead than said tapered threads to facilitate the removal of the bit from the cou- Dling.

' FREDERICK K. LANDGRAF.

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