US3648788A

US3648788A - Drilling apparatus

Info

Publication number: US3648788A
Application number: US52413A
Authority: US
Inventors: John R Mckinney
Original assignee: MCKINNEY DRILLING CO
Current assignee: MCKINNEY DRILLING CO
Priority date: 1970-07-06
Filing date: 1970-07-06
Publication date: 1972-03-14
Anticipated expiration: 1989-03-14

Abstract

A drilling apparatus having a drill string with drill body attached extending into the bottom of a bore hole. The drill body carries a drill bit which is cutting into a drilling face. The lower portion of the bore hole is filled with drilling fluid which is recirculated therein. Compressed gas is supplied from the surface through the drill string to a manifold in the drill body to operate two eductor systems. The first system educts drilling fluid into a plurality of airstreams and then directs jets of this mixture against the drill bit and the drilling face, and the second system removes the mixture of gas, drilling fluid and cuttings from the drilling face. Cuttings are collected in a basket annularly disposed about the drill body.

Description

. i W H a MW i ite [151 3,648,788

Meihhey Mar, M, W

[54] DRILLING AlPlP'AlltfitT Ufi 2,849,214 8/1958 Hall ...l75/324 [72] Inventor: John M McKinney Gainesville Va 2,880,965 4/1959 Bobo ..l75/69 [73] Assignee: Mcliinney Drilling Compimy Primary Examiner-James A. Leppink I Film: m y 1970 Attorney Bll'Ch Swmd er McKle & Beckett [2|] Appl. No: 52,413 ABSTRACT A drilling apparatus having a drill string with drill body at- 521 U.S.Cll ..175/205, 175/69 thched extending the hotwm of a bore hole- The hill [51 1 lint. cl ..lE2l|b 21/88 body carries a hill hit which is cutting a dfilhhg face- The {58] Field oi Search 175/205, 308, 208, 422, 69, the We is with drilling fluid which 175 324; 166 105 1051 1053, 1054; 173 74 is recirculated therein. Compressed gas is supplied from the l l surface through the drill string to a manifold in the drill body [56] References (med to operate two eductor systems. The first system educts drilling fluid into a plurality of airstreams and then directs jets UNITED STATES PATENTS of this mixture against the drill bit and the drilling face, and the second system removes the mixture of gas, drilling fluid 2,660,250 1 1/1953 Gage et al 175/308 and Cuttings f the drilling face Cuttings are collected i 3 2,819,038 1/1958 Ecke] "175/308 basket annularly disposed about the drill body. 2,035,350 3/1936 Stoll...... ..l75/308 1,525,235 2/1925 Hansen 175/308 20 Unims, 4 Drawing Figures PATENTEUHAR 14 m2 SHEET 1 BF 2 INVENTOR JOHN R. McKINNEY ATTORNEYS PAIENTEDMAR 14 I972 sum 2 [1F 2 INVENTOR JOHN R. MCKINNEY f ATTORNEYS lDlltlllLlLllNG APPARATUS BACKGROUND OF THE INVENTION 1. Field This invention relates generally to apparatus for drilling bore holes and more particularly to a drilling apparatus in which the drill bit and drilling face are kept clean, and the cuttings removed by mechanisms operated by compressed gas.

2. Prior Art The drilling of large bore holes for various purposes, and particularly rock drilling of large diameter shafts, caissons and the like, has become a highly developed art. As the drilling has become more demanding, so has the need for apparatus which is capable of prolonged operation in an efficient economical, and reliable manner. Generally, bore holes are drilled by means of a drill bit cutting into a drilling face at the bottom of the bore hole. The drill bit is attached to a drill string that extends to the surface. Among the problems encountered in drilling are cooling the drill bit, removing the drill cuttings from the bore hole, and keeping the drill bit and drilling face clean. In order to alleviate such problems, a drilling fluid is usually introduced into the hole in the form of a liquid having characteristics especially suited for the particular type of drilling. In many prior art devices this drilling fluid is continuously recirculated to and from the surface, and is additionally utilized as a carrier to remove to the surface the cuttings generated during drilling. In order to circulate the drilling fluid through the bore hole with sufficient velocity to move the suspended cuttings to the surface, the prior art systems require pumps located on the surface. These pumps are expensive and are characterized by low reliability. The stream of circulating drilling fluid generated by such pumps frequently is not suffi ciently powerful to continuously clean the drill bit and drilling face, to the extent necessary for efficient operation so this problem remains.

in other of the prior art devices, drilling fluid is not pumped to the surface, but is recirculated in the bottom of the bore hole. Cuttings are removed from the bottom of the bore hole by this circulating fluid and are then captured in various ways for separate removal. These systems utilize pumps installed within the bore hole for recirculating the drilling fluid, and such pumps suffer greatly from the environmental conditions present in the bore hole and are unreliable over prolonged periods of operation. In addition, these pumps tend to foul with the cuttings and contaminated drilling fluid. Again, the serious problem of continuously cleaning the drilling face and the drill bit is not solved by these devices, for they are not directed toward this end.

SUMMARY OF THE INVENTION This invention presents a new and novel apparatus for solv ing the problems present in the devices of the prior art. At the bottom of a drill string rotating in a bore hole is a drill body which has a drill bit cutting into a drilling face. The drill body operates in a supply of drilling fluid which is put into the bottom of the bore hole and which may be any conventional drilling fluid or mud. A collection basket is carried by said drill body above said drill bit. The drill body has an interior discharge passageway extending longitudinally therein, which passageway has an inlet adjacent the drill bit in communica tion with the bottom of the bore hole and an outlet spaced above the drill bit and directed into the collection basket. Conduit means is carried by the drill body outside of the discharge passageway, which conduit means has inlet means communicating with the lower portion of the bore hole outside of the drill body and outlet means communicating with the bottom of the bore hole adjacent the drill bit. Pump means is carried by the drill body to conduit drilling fluid from the bore hole downwardly through the conduit means into the bottom of the bore hole adjacent the drill bit and to conduct drilling fluid and cuttings from the bottom of the bore hole upwardly through the discharge passageway to the collection basket which is constructed to permit the drilling fluid deposited therein to return to the bottom of the bore hole for recirculation.

Contained in the drill body are systems which clean the drill bit and drilling face, agitate and suspend the drill cuttings and remove the cuttings from the area of the drilling face. A first system mixes drilling fluid and compressed gas and then directs the mixture thus formed in a jet against the drill bit and the cutting face. This mixture of high pressure gas and drilling fluid is extremely active and creates a. great deal of turbulence which cleans the drilling face and the drill bit, so that the drill bit constantly has new rock against which to operate. The turbulence also insures that the cuttings are agitated and remain in suspension, so they can be easily removed from the area.

A second system continuously pulls the turbulent mixture of gas, drilling fluid and cuttings from the area of the drilling face. The mixture is propelled upwardly by the force of an eductor plus the compressed gas bubbles present in the mixture to a series of separator tubes, where the gas is allowed to escape upward to the surface, while the cuttings settle into a collection basket. At periodic intervals, the entire drill string is removed from the hole and the basket is emptied.

It is an object of this invention to provide an improved drilling apparatus in which a turbulent jet mixture of compressed gas and drilling fluid is used to continuously clean the drill bit and the cutting face.

Another object of this invention is to provide an improved drilling apparatus in which drill cuttings are continuously and positively removed from the area of the drilling face.

Another object of this invention is to provide an improved drilling apparatus in which gas operated mechanisms are used to clean the drill bit and drilling face and to remove the cuttings therefrom.

Another object of this invention is to provide an improved drilling apparatus in which the drilling fluid is continuously recirculated in the bottom of the bore hole.

Another object of this invention is to provide an improved drilling apparatus in which the drill cuttings are collected in a basket mounted on the drill body.

Another object of this invention is to provide an improved drilling apparatus which is efficient, economical and reliable over extended periods of time.

DESCRIPTION OF THE DRAWINGS FIG. l is an elevational showing of a drill body in accordance with the instant invention. FIG. 2 is an elevation, partially in section, of the lower portion of the drill body of FIG. ll.

FIG. 3 is an elevation, partially in section, of the upper portion of the drill body of FIG. ll.

FIG. 4 is a bottom view of the drill body of FIG. 3.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, there is shown a bore hole it) having a drill face lll. Operating within bore hole 10 is a vertical drill body ll2. At the lowermost end of drill body I2 is a drill bit 13 with a plurality of rolling cutters l4. Cutters Ml cut into drilling face 11 when drill body 12 is rotated and generate from this a continuous stream of drill cuttings 15. Bore hole 10 is filled to a predetermined depth with drilling fluid i6. Drill body 12 is attached to a hollow drill string 17, which extends to the surface, by means of a gas supply tube 18, which is coaxial with drill body 12 and forms the structural backbone of drill body 12. Machinery on the surface at the top of the bore hole (not shown) rotates drill string 17 and thereby drill body 12 rotates also. Tube 13 conducts compressed gas from drill string 17 to an annular compressed gas manifold 22 positioned immediately above drill bit 13 in the lower portion of drill body 12. Communicating with compressed gas manifold 22 by means of conduits 24 are a plurality of compressed gas operated drilling fluid eductors 25, which protrude downwardly through the disc-shaped top 23 of drill bit 13. Each eductor 25 has a drilling fluid inlet 26 located above top 23 and a nozzle 27 beneath top 23 and adjacent to and directed toward cutters 14 and drilling face 11. Eductor 25 can be any of the well known types such as a venturi type. Drilling fluid inlet 26 is separated from the area of drill bit 14 by top 23, so that inlet 26 is educting relatively clean drilling fluid 16. However, inlet 26 is also equipped with a filter screen 28.

As shown in detail in FlGS. 2 and 3, compressed gas manifold 22 also communicates by means of a plurality of gas passages 29 with an extraction eductor 30 which is centrally positioned at the base of supply tube 18 and is actually surrounded by manifold 22. Extraction eductor 30 has an inlet 31, communicating with the area in which drill bit 13 is operating,- of a discharge conduit 32 mounted internally of and coaxially with outer tube 18. Eductor 30 pulls the mixture of compressed gas, drilling fluid, and cuttings from the area of drill bit 13 and drilling face 11. Discharge conduit 32 terminates at its upper end in a distributor 33 having a plurality of distributor pipes 34 at right angles to the axis of conduit 32. A plurality of open ended vertically oriented cylindrical separator tubes 36 having top openings 37 and bottom openings 38 receive the discharge from distributor pipes 34 through openings 35 in the sides of tubes 36. Distributor tubes 34 discharge into separator tubes 36 at 90 to the axis of tubes 36.

Disposed coaxially about tube 18 and spaced therefrom is a cuttings collection basket 40. Basket 40 is removably mounted upon a basket base 41 which has a sloping bottom 42. Affixed to passage 18 are a plurality of radially oriented centering vanes 43 which engage the sides of basket 40. The operation and the interaction of centering vanes 43 will hereinafter be explained. Basket 40 is positioned beneath separator tubes 36 to catch the drilling fluid 16 and cuttings l exiting through bottom openings 38.

FIG. 2 shows a detail of a preferred arrangement of the various systems set forth in the invention. To continuously clean cutters l4 and drilling face 11, and to agitate and suspend cuttings 15, jets of high velocity compressed gas and drilling fluid emanate from the plurality of nozzles 27, in this case three, which are immediately adjacent to and aimed to sweep across cutters l4 and drilling face 11. As shown, one of the nozzles 27 is inclined about degrees in the direction of rotation of the drill bit 13. The other two nozzles 27 are shown inclined about 10 toward the central axis of the drill bit. Other orientations and specific inclinations may be employed. To produce each of the pressure jets from the nozzles 27, a portion of the compressed gas in manifold 22 is bled through conduits 24 to operate eductors 25, each of which has a venturi section 45. The low pressure area created adjacent venturi 45 causes drilling fluid 16 to be drawn in through inlet 26 and mixed with the high velocity compressed motivating gas. Screen 28 is provided to insure that debris is not drawn into this high velocity stream and impacted against cutters 14. Nozzles 27 direct the high velocity jet toward cutters 14 and drilling face 11 at close range to insure that particles which adhere to the surface of cutters 14 are removed and that drilling face 111 is continuously swept clean of cuttings. In this manner drilling face 11 constantly presents a clean surface on which cutters 14 can operate effectively.

Continuing in reference to HO. 2, other streams of compressed gas are directed from manifold 22 through a series of motivating fluid inlets 29 which inject a plurality of compressed gas jets around the periphery of evacuation eductor 30 to create a low pressure area in evacuation eductor 30 in the known manner. The inlets 29 are inclined inwardly at an angle of about and in addition are tapered slightly inwardly from bottom to top. In the device shown there are four inlets 29 spaced circumferentially 90 degrees apart. Eductor draws through intake 31 the turbulent mixture of gas, drilling fluid 16 and cuttings 15 from the area of drilling face l1, and delivers this mixture swiftly upward through discharge conduit 32.

A study of the complete operation of a device constructed in accordance with the instant invention will illustrate the advantages of the particular interrelationship of elements. Drill string 17, having attached thereto drill body 12 and drill bit 13, is lowered into the bottom of bore hole 10 and submerged in a predetermined amount of drilling fluid 16. As an example, with a drill body that is 16 feet long, 8 to 10 feet of drilling fluid is effective, but other quantities of fluid can be used. When drill bit 13 contacts drilling face 11 and drill string 17 is rotated, compressed gas is continuously supplied to manifold 22 by means of the hollow drill string 17, through the tube 18. A portion of the compressed gas in manifold 22 is bled off to a series of eductors 25 which educt drilling fluid 16 into the compressed gas stream, creating a high velocity turbulent mixture which is directed toward cutters 14 and drilling face 11 at close range by means of nozzles 27. The jets of compressed gas and drilling fluid 16 are far more effective to clean drill bits 14 and drilling face 11, and to agitate and suspend cuttings 15, than would be jets of drilling fluid 16 alone, since they create a great deal more turbulence and bubbling cleansing action. Positioning nozzles 27 immediately adjacent the drill bit 14 and drilling face 11 renders the full force of the jets effective.

The action of the jets of high pressure gas and drilling fluid 16 is complemented by the positive exhaust of the centrally mounted evacuation eductor 30, also operated by strams of compressed gas from manifold 22, which continuously evacuates the mixture of gas, drilling fluid l6 and cuttings 15 from the area of drilling face 11. The force of evacuation eductor 30, plus the turbulence created by the bubbles of gas entrained in the mixture, keeps cuttings 15 in suspension and carries the mixture swiftly through the discharge passageway which extends through discharge conduit 32 to distributor 33, thence through openings 35 into separator tubes 36. The abrupt change in direction of flow and resulting turbulence in separator tubes 36 allows the gas to escape upward through top openings 37, while the drilling fluid 16 and cuttings 15 drop downward through bottom openings 38 into collection basket 40. In the course of operation, basket 40 will fill to the top with drilling fluid 16 which then continuously spills over to the bottom of the bore hole 10, where his again inducted into the system through inlets 26.

At periodic intervals, the entire apparatus is removed from bore hole 10, and at that time collection basket 40 can be emptied. Owing to the novel construction of basket 40, which simply rests on its base 41, basket 40 need only be raised slightly from base 41 to allow the cuttings 15 which have been deposited therein to drop out the bottom by action of inclined surface 42. Centering vanes 43 insure that the basket is properly aligned and reseated.

This invention provides a drilling apparatus in which a great deal of turbulence is created in the area of drilling face 11 in order to continuously clean cutters 14 and drilling face 11. Complementing this action is a means for evacuating the cuttings from the area of drilling face 11. The combination of these two systems causes a positive, forced circulation of a turbulent mixture through the area of the drilling face, thus providing a more efiicient and reliable drilling apparatus. In the preferred embodiment described above the entire mechanism has no moving parts, except for cutters 14, which may be of any known type. The novel means for separating the gas and cuttings 15 is simple and reliable, and has little chance of becoming clogged or otherwise malfunctioning. Collection basket 40 is unique, for its requires a minimum of effort to empty and is self-cleaning, a great advantage in machinery of this large size. Basket 40 can be equipped with holes or screens (not shown) through which the drilling fluid 16 may drain away for recirculation, these holes or screens being of such size as to continuously remove smaller particles that might otherwise be carried along and recirculated with drilling fluid 16. Such cleaning screens could obviously be provided at other points within the system. Other means for supplying the mixture of gas and drilling fluid to nozzles 25, such as mechanical pumps, could be used with this apparatus, as could other means for evacuating mixture of gas, drilling fluid lb, and cuttings 115 from the area of drill face 111.

With this invention, the drilling fluid is permitted to rest relatively non turbulently in the bore hole outside of the drill body. An annular skirt depending from the disc-shaped top 23 tends to confine the turbulent mixture of drilling fluid, gas and cuttings in the area of the drill bits. Thus, this turbulent mixture is prevented from rising outside of the drill body and is directed into the inlet 31 of the exhaust passageway. The cuttings are thus confined to the relatively small exhaust passageway from which collection of the cuttings may be made more effectively than would be possible if the discharge mixture of drilling fluid, gas and cuttings were elevated from the drilling area through the relatively large space outside of the drill body. Moreover, substantially less power is required to discharge such mixture through the interior passageway rather than the space outside of the drill body.

it is to be understood that while preferred forms of the invention are herein illustrated and described, it is not to be limited to specific forms or arrangements of parts herein described and shown. The scope of the invention is to be determined by the claims.

lclaim:

1i. Apparatus for drilling a bore hole having a drilling face and a supply of drilling fluid therein comprising a drill string extending into said bore hole,

a drill body attached to drill string,

a drill bit carried by said drill body and having cutters operating in said drilling fluid, said cutters engaging said drilling face and generating cuttings therefrom,

a plurality of nozzles in said drill body adjacent to said cutters and said drilling face and directed theretoward,

means for continuously supplying a mixture of compressed gas and drilling fluid through said nozzles to clean said cutters and said drilling face and to agitate and suspend said cuttings, said means including a plurality of compressed gas operated drilling fluid eductors in communication with said bore hole and educting drilling fluid therefrom, and

evacuating means for removing said mixture of gas, drilling fluid and cuttings from adjacent said drilling face.

2. The apparatus of claim ll wherein said means for supply ing a mixture of compressed gas and drilling fluid and said evacuating means are motivated by compressed gas.

3. The apparatus of claim 2 further comprising means carried by said drill string adjacent said drill body for separating said cuttings from said mixture of gas, drilling fluid and cuttings, and means carried by said drill string adjacent said drill body for collecting said cuttings.

d. The apparatus of claim 3 wherein said means for collecting said cuttings comprises a collection basket carried by said drill body and in communication with said means for separating said cuttings, said collection basket including a base portion having a downwardly and outwardly sloping bottom and a generally cylindrical side portion supported by said base portion and axially separable therefrom, whereby said cuttings will be ejected from said collection basket by action of said sloping bottom when said side portion is separated axially from said base portion.

5. Apparatus for drilling a bore hole having a drilling face and a supply ofdrilling fluid therein comprising a drill string extending into said bore hole,

a drill body attached to said drill string,

means for continuously supplying a mixture of compressed gas and drilling fluid through said nozzles to clean said cutters and said drilling face and to agitate and suspend said cuttings, said means comprising a compressed gas supply passage carried by said drill string, a compressed gas manifold in said drill body communicating with said gas supply passage by means of a gas supplytube, and a plurality of compressed gas operated drilling fluid eductors, each of said eductors having a gas inlet in communication with said compressed gas manifold, an eduction inlet in communication with said bore hole to educt drilling fluid, and an outlet communicating with said nozzle, and

6. The apparatus of claim 5 wherein said drill bit further comprises a disc-shaped top covering said cutters, and wherein said drilling fluid eductors protrude through said top, said eduction inlets being above said top and said outlet communicating with said nozzles below said top.

7. The apparatus of claim 5 wherein said evacuating means comprises a compressed gas operated evacuation eductor having a gas inlet in communication with said compressed gas manifold, an eduction inlet adjacent to said drill bit, and a discharge conduit, whereby the mixture of gas, drilling fluid, and cuttings is educted from the area adjacent said drill bit and passed into said discharge conduit.

8. The apparatus of claim 7 further comprising means carried by said drill string adjacent said drill body for separating said cuttings from said mixture of gas, drilling fluid and cuttings, and

means carried by said drill string adjacent said drill body for collecting said cuttings.

9. The apparatus of claim 8 wherein said means separating said cuttings comprises a distributor communicating with said eductor discharge conduit,

a plurality of generally vertically oriented cylindrical separator tubes having open tops and open bottoms communicating with said distributor through openings in the wall of said separator tubes, said separator tubes being oriented perpendicular to the direction of discharge of said distributor, whereby the turbulence in said separator tubes allows said gas to escape upward through said open tops while said cuttings and said drilling fluid exit downward through said open bottoms,

and wherein said collecting means comprises a collection basket positioned beneath said open bottoms of said separator tubes.

W. The apparatus of claim 9 wherein said evacuation eductor and said discharge tube are centrally located in and coaxial with said drill body, wherein said compressed gas manifold is circumferentially disposed about said evacuation eductor, and wherein said gas supply tube is coaxia'lly disposed about said evacuation eductor discharge tube.

ill. The combination of claim wherein said distributor is perpendicular to the axis of said evacuator discharge tube, and wherein said collection basket is disposed about and coaxial with said drill body.

112. The apparatus of claim ll wherein said collection basltet comprises a base portion attached to said drill body and having a bottom sloping downwardly and outwardly from the center thereof,

a generally cylindrical side portion supported by said base portion and axially separable therefrom, and

a plurality of collection basket centering vanes attached to said drill body and extending radially outwardly therefrom to contact said side portion.

l3. An apparatus for drilling a bore hole and recirculating a drilling fluid contained in the lower portion of the bore hole which comprises:

a drill body adapted for suspension from a drill string,

a drill bit carried by said drill body at the bottom thereof and having cutting means operable in the drilling fluid,

a collection basket carried by said drill body above said drill bit,

said drill body having an interior discharge passageway extending longitudinally therein, said passageway having an inlet adjacent said drill bit in communication with the bottom of the bore hole and an outlet spaced above said drill bit and directed into said collection basket,

conduit means carried by said drill body outside of said passageway, said conduit means having inlet means communicating with the lower portion of the bore hole outside of said drill body and outlet means communicating with the bottom of the bore hole adjacent said drill bit,

pump means carried by said drill body to conduct drilling fluid from the bore hole downwardly through said conduit means into the bottom of the bore hole adjacent said drill bit and to conduct drilling fluid and cuttings from the bottom of the bore hole upwardly through said discharge passageway to said collection-basket, said basket being constructed to permit the drilling fluid deposited therein to return to the bottom of the bore hole for recirculation.

14. The apparatus of claim 13 wherein said conduit means comprises a plurality of conduits spaced circumferentially around said drill body and said outlet means comprises a plurality of nozzles. I

15. The apparatus of claim 14 wherein said pump means includes a plurality of gas operated eductors in said conduits.

16. The apparatus of claim 15 wherein said pump means further includes a gas operated eductor in said passageway.

17. The apparatus of claim 13 wherein said pump means comprises a plurality of pumps in said conduit means and said passageway.

18. The'apparatus of claim 17 wherein each of said pump means comprises a gas operated eductor.

19. The apparatus of claim 13 wherein said pump means comprises gas operated eductor means.

20. The apparatus of claim 19 wherein said passageway outlet comprises means to separate the gas from the drilling fluid and cuttings.

Claims

1. Apparatus for drilling a bore hole having a drilling face and a supply of drilling fluid therein comprising a drill string extending into said bore hole, a drill body attached to drill string, a drill bit carried by said drill body and having cutters operating in said drilling fluid, said cutters engaging said drilling face and generating cuttings therefrom, a plurality of nozzles in said drill body adjacent to said cutters and said drilling face and directed theretoward, means for continuously supplying a mixture of coMpressed gas and drilling fluid through said nozzles to clean said cutters and said drilling face and to agitate and suspend said cuttings, said means including a plurality of compressed gas operated drilling fluid eductors in communication with said bore hole and educting drilling fluid therefrom, and evacuating means for removing said mixture of gas, drilling fluid and cuttings from adjacent said drilling face.

2. The apparatus of claim 1 wherein said means for supplying a mixture of compressed gas and drilling fluid and said evacuating means are motivated by compressed gas.

4. The apparatus of claim 3 wherein said means for collecting said cuttings comprises a collection basket carried by said drill body and in communication with said means for separating said cuttings, said collection basket including a base portion having a downwardly and outwardly sloping bottom and a generally cylindrical side portion supported by said base portion and axially separable therefrom, whereby said cuttings will be ejected from said collection basket by action of said sloping bottom when said side portion is separated axially from said base portion.

5. Apparatus for drilling a bore hole having a drilling face and a supply of drilling fluid therein comprising a drill string extending into said bore hole, a drill body attached to said drill string, a drill bit carried by said drill body and having cutters operating in said drilling fluid, said cutters engaging said drilling face and generating cuttings therefrom, a plurality of nozzles in said drill body adjacent to said cutters and said drilling face and directed theretoward, means for continuously supplying a mixture of compressed gas and drilling fluid through said nozzles to clean said cutters and said drilling face and to agitate and suspend said cuttings, said means comprising a compressed gas supply passage carried by said drill string, a compressed gas manifold in said drill body communicating with said gas supply passage by means of a gas supply tube, and a plurality of compressed gas operated drilling fluid eductors, each of said eductors having a gas inlet in communication with said compressed gas manifold, an eduction inlet in communication with said bore hole to educt drilling fluid, and an outlet communicating with said nozzle, and evacuating means for removing said mixture of gas, drilling fluid and cuttings from adjacent said drilling face.

8. The apparatus of claim 7 further comprising means carried by said drill string adjacent said drill body for separating said cuttings from said mixture of gas, drilling fluid and cuttings, and means carried by said drill string adjacent said drill body for collecting said cuttings.

9. The apparatus of claim 8 wherein said means separating said cuttings comprises a distributor communicating with said eductor discharge conduit, a plurality of generally vertically oriented cylindrical separator tubes having open tops and open bottoms communicating with said distriButor through openings in the wall of said separator tubes, said separator tubes being oriented perpendicular to the direction of discharge of said distributor, whereby the turbulence in said separator tubes allows said gas to escape upward through said open tops while said cuttings and said drilling fluid exit downward through said open bottoms, and wherein said collecting means comprises a collection basket positioned beneath said open bottoms of said separator tubes.

10. The apparatus of claim 9 wherein said evacuation eductor and said discharge tube are centrally located in and coaxial with said drill body, wherein said compressed gas manifold is circumferentially disposed about said evacuation eductor, and wherein said gas supply tube is coaxially disposed about said evacuation eductor discharge tube.

11. The combination of claim 10 wherein said distributor is perpendicular to the axis of said evacuator discharge tube, and wherein said collection basket is disposed about and coaxial with said drill body.

12. The apparatus of claim 11 wherein said collection basket comprises a base portion attached to said drill body and having a bottom sloping downwardly and outwardly from the center thereof, a generally cylindrical side portion supported by said base portion and axially separable therefrom, and a plurality of collection basket centering vanes attached to said drill body and extending radially outwardly therefrom to contact said side portion.

13. An apparatus for drilling a bore hole and recirculating a drilling fluid contained in the lower portion of the bore hole which comprises: a drill body adapted for suspension from a drill string, a drill bit carried by said drill body at the bottom thereof and having cutting means operable in the drilling fluid, a collection basket carried by said drill body above said drill bit, said drill body having an interior discharge passageway extending longitudinally therein, said passageway having an inlet adjacent said drill bit in communication with the bottom of the bore hole and an outlet spaced above said drill bit and directed into said collection basket, conduit means carried by said drill body outside of said passageway, said conduit means having inlet means communicating with the lower portion of the bore hole outside of said drill body and outlet means communicating with the bottom of the bore hole adjacent said drill bit, pump means carried by said drill body to conduct drilling fluid from the bore hole downwardly through said conduit means into the bottom of the bore hole adjacent said drill bit and to conduct drilling fluid and cuttings from the bottom of the bore hole upwardly through said discharge passageway to said collection basket, said basket being constructed to permit the drilling fluid deposited therein to return to the bottom of the bore hole for recirculation.

14. The apparatus of claim 13 wherein said conduit means comprises a plurality of conduits spaced circumferentially around said drill body and said outlet means comprises a plurality of nozzles.

18. The apparatus of claim 17 wherein each of said pump means comprises a gas operated eductor.