US 2969846 A
Description (OCR text may contain errors)
PERCUSSIVE DRILL: BIT FOR USE IN REVERSE FLOW FLUSHING IN SOFT ROCK DRILLING Filed D90. 16, 1958 Jan. 31, 1961 R SANDVIG 2 969,846
I N VE N TOR. wafer L 5/7/l/0V/G' United tates Patent C PERCUSSIVE DRILL BIT FOR USE IN REVERSE FLOW FLUSHING IN SOFT ROCK DRILLING Robert L. Sandvig, Whittier, Calif., assignor to Thor Power Tool Company, Aurora, 111., a corporation of Delaware Filed Dec. 16,1958, Ser. No. 780,745
2 Claims. (Cl. 175-418) The present invention relates to drill bits in general and more particularly to a drill bit specially designed for percussive drilling in moist rock formations and utilizing suction air for the removal of cuttings.
The present application is a continuation-in-part of my co-pending application for United States Letters Patent, Serial No. 618,748, filed October 29, 1956, for Drill Bit, now Patent 2,890,021. The construction therein shown and claimed has proven highly successful for its intended purposes, but is not entirely satisfactory for use in drilling moist and softer rock formations owing to the tendency of the cuttings to become impacted in pellets not readily entrained in the suction air stream. The reason for this is not fully understood, but it is believed that softer rock may, and usually does, contain considerable amounts of moisture. Consequently, the disintegration of the rock into fine particles by the percussive action of the drill bit may result in the adherence and compacting of these into lumps owing to their moisture content. Furthermore, the cuttings tend to collect rapidly as the drill advances into soft rock and the closely overlying fiat end surfaces of the drill bit act to press these particles together into accumulation so large the air stream fails at times to entrain them for removal. This is particularly true as respects cuttings located radially inward of the outer periphery of the inlets to the suction air passage. interferes with the operation and efiiciency of the drill.
It has been found that if certain changes are made in the drill bit design, the objectionable characteristics of the drill referred to above are obviated and there is avoided an accumulation of suflicient cuttings as to interfere with their suction removal using the same air flow and the same suction and filtering system employed with the percussive driving unit in drilling hard rock formations. These results are achieved by the simple expedient of relieving the inlet end of the suction air passages in the areas thereof adjacent the cutting face of the drill bit. Although the relief required may take various forms, it is found that particularly satisfactory results are obtained using a semi-circular cutout having a generally flat end face parallel to the end face of the drill bit and an arcuate shaped side wall having its midportion lying generally tangent to the innermost peripheral edge of the suction air inlet, a relationship clearly illustrated in the drawing accompanying this specification. The shallow, semi-circular chamber thus provided at the entrance to the air inlet cooperates with the high velocity air stream flowing radially inward from the side wall of the bore to pick up the cuttings and to channel them toward the suction air passages quickly and without allowing the cuttings to accumulate in sufficient quantity to become impacted by the percussive movement of the drill bit.
Accordingly, it is a primary object of the present invention to provide an improved percussive type drill bit utilizing suction air to remove cuttings and specially designed for use in drilling moist rock formations.
Another object of the invention is the provision of an The excessive accumulation of cuttings seriously ice improved percussive type drill bit utilizing suction air removal of cuttings and having specially designed cutting inlet ports so arranged that the high velocity air flow therethrough is effective to entrain the cuttings from the cutting face before these can accumulate in masses too large for eflicient removal by suction air.
These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.
Referring now to the drawing in which a preferred embodiment of the invention is illustrated:
Figure 1 is a general schematic view of a percussive drill tool utilizing suction air for the removal of cuttings and showing a drill incorporating the features of the present invention in operation in a bore hole;
Figure 2 is an end view on an enlarged scale of the drill bit taken along plane 22 on Figure 1;
Figure 3 is a fragmentary enlarged sectional view taken along line 33 on Figure 1; and
Figure 4 is a still larger cross-sectional view of the drill bit taken along line 4-4 on Figure 2. 7
Referring more particularly to Figure 1, there is shown a conventional pneumatically driven power tool designated generally 10 operated by pressurized air supplied through a flexible hose 11. Tool 10 includes a main body 12 housing therewithin reciprocal piston and hammer means for imparting sharp powerful axial thrusts to a hollow drill steel 13 adapted to be detachably chucked in the lower end 14 of the tool. The constructional details of tool 10 form no part of the present invention and are disclosed in full in my co-pending application for United States Letters Patent Serial No. 636,311, filed January 25, 1957, entitled Drill System With Suction. This power unit includes means utilizing a portion of the pressurized air supplied through hose 11 to operate an ejector assembly 16 mounted in backhead 17 of the tool. The ejector inlet is in communication with a suction air passage extending longitudinally and centrally through the drill tool and through the hollow drill steel 13. The discharge end of ejector assembly 16 opens into a flexible hose 18 discharging into any suitable cuttingsand-air separator 20. Preferably this separator or filter is of the multi-stage type to the end that both large and fine cuttings may be removed rapidly and with maximum efliciency.
It will be understood that drill steel 13 may include several sections suitably connected togetther as by a fluted coupling sleeve 23, the flutes 24 serving to admit large quantities of atmospheric air to bore hole 25.
As appears more clearly in Figures 3 and 4, the lower ends of the drill steel sections are provided with a Morse taper 26 seating snugly against a correspondingly tapered side wall 27 of a well opening through one end of drill bit 28. Each drill steel is provided with a suction air passage 29 opening into the bottom of well 30 in drill bit 28, as is best shown in Figure 4.
Drill bit 28 comprises a cup-shaped main body having upwardly and rearwardly inclined exterior wall 31 extending from the foremost end wall 32 thereof to its inlet end. End wall 32 lies substantially at right angles to the longitudinal axis of the bit body and has securely and fixedly mounted therein, as by brazing, welding or the like, a plurality of radially disposed cutting elements 33, 33 of suitable abrasion resistant material. The sectors formed by and between the cutting elements are in communication with central bore 29 of the drill steel and well 30 of the bit body by way of upwardly and inwardly converging bores forming air ducts 34, 34.
The lower or inlet ends 35 of ducts 34 open into semicircular recesses 36 in the manner clearly illustrated in Figures 2 and 4. The radial entry to recesses 36 are 'flush with the edge of flats 37 lying generally parallel to the axis of bit body 28 in the area thereof between cutting, elements 33, 33. These flats cooperate .with the adjacent side wallsof bore hole 25 to provide shallow passages assuring high velocity air flow into recesses 36 and into close proximity to the cuttings formed by elements 33, 33. The down flowing air is diverted inwardly and upwardly through recesses 36 into ducts 34' and main suction air passageway 29 leading through the drill' tool and to filter assembly 20. It is pointed out that the arcuate back wall of recesses 36 cooperates with the adjacent side wall portions of ducts 34 to divert the air into the latter as it picks up dust and other cuttings from the bore hole face. The depth of recesses 36 longitudinally of the drill bit taken with the distance between the bore base and end face 32 of the drill bit is that found to prevent compaction of moist cuttings and the formation of particles too large to be entrained by the air stream and may be varied from the proportions illustrated advantageously for best results in a particular rock formation.
While the particular percussive rock bit herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of. construction or design herein shown other than as. defined in the appended claims.
1". A percussive type rock bit adapted tobe operated with suction applied to the central bore thereof and. particularly suitable for use in drilling softer rock formations wherein the cuttings have a tendency to cake at the drill tip and form chunks not readily entrained in the suction air stream, said rock bit comprising a solid metal body having a flat end. wall normal to the axis of said body, the side walls of said body converging rear-wardly from said end wall in a gradual taper and having radially shallow flats distributed circ'umferentially of said end wall providing high velocity suction air passages adapted to convey chip pick-up air to the drill bit, said end wall having a plurality of radially disposed cutting. elements secured thereto and projecting axially beyond said end wall, said bit body having, a central suction air passage opening through one end and terminating short of said flat end wall, a plurality of relatively small diameter suction air passages inclined to the axis of said drill body and leading from the bottom of said central air passage to inlets positioned one between each pair of said cutting elements and closely adjacent the merger of said shallow flats with the peripheral rim of. said end wall, said drill bit being characterized in that a major portion of said tip end wall to either side of'the inlet of each of said last-mentioned air passages is cut away for a substantial distance axially of the bit body to provide high velocity flow passages for cuttings which flow passages are located out of the'irnpact area and directly in the high velocity suction air passage.
2. In an article of manufacture of the type comprising a drill bit adapted to be detachably mounted on the end of a hollow drill steel forming part of a percussive rock drilling unit operable to remove rock cuttings continuously in a high velocity suction air stream flowing inwardly through the bore hole and outwardly through the hollow drill steel and particularly suitable for use in-drilling softer rock formations wherein the cuttings have a tendency to' agglomerate at the drill tip and form chunks not readily entrainedin the suction air stream, said drill bit being of the type having a solid one-piece body provided with an axial well for seating the drill steel, the exterior of one end wall of said body being generally normal to the body axis and having secured thereto a plurality of radially disposed cutting elements, a suction air duct leading from a point between each of said cutting elements into said axial well, the inlet ends of said suction air ducts being recessed axially thereof sufiieiently to provide wide but shallow high velocity pass-ages' opening through the side wall of said body and effective to convey air at high velocity into said ducts along with rock cuttings produced by the cutting elements to either side thereof, thereby to facilitate the flow of cuttings away from said elements and avoiding the compactingof the same opposite the end wall of said percussively-driven drill bit body.
References Cited in the file of this patent UNITED STATES PATENTS Bedford Dec. 26, 1933 Nater Feb. 7, 1956