US2258352A - Core drill - Google Patents

Description

Oct. 7, 1941. A. c. CATLAND ETAL CORE DRILL Filed Nov. 27, 1939 2 Sheets-Sheet 1 p 5 a 5 a; i WM 8 2 f: :1: my. W my m Z/ Z F I. w wCxC M r .q ,1 5 P a "M W fi A. Ha E i w A w d a. un MM g 2 4 a 7 a /2 wk 5 a w; 54w if? p Z, i, J i/ 2% i, h 427%/ A Q. 6 M1000 o 0 L O 7 /A%/wv a/A 4V 4% 12 k 1: 424 5/ 4 a 4 via Oct ,1 A. c. CATLAND ETAL 2,258,352

CORE DRILL Filed Nov. 27, 1939 2 Sheets-Sheet 2 Patented Oct. 7, 1941 CORE DRILL Alfred C. Catland, Alhambra, and Philip C.

Efromlon, Whittier, Calif., assignors 'of onehalf to Globe Oil Tools Company, Los Nietos, Calii'., a corporation of California Application November 27, 1939, Serial No. 306,260

9Claims.

This invention relates to well drilling tools and relates more particularly to a core drill for use in the rotary method of well drilling. A general object of this invention is to provide a practical,

effective, and dependable core drill of the type in which the core barrel may be withdrawn on a wire line or cable.

Another object of this invention is to provide a core drill having a core receiving barrel adapted to be removed on a wire line and embodying novel means for releasably latching or retaining the barrel in the core receiving position.

Another object of this invention is to provide a core drill of the character mentioned in which the barrel retaining or latching means is located at the upper end of the barrel and is constructed to securely latch the barrel against upward movement and to be readily released by a retrieving tool lowered through the drilling string.

Another object of this invention is to provide a core drill of the character mentioned in which the core receiving barrel is free to "float" or to remain non-rotatable during the coring operation.

Another object of this invention is to provide a core drill of the character mentioned embodying a plug bit for cutting away the central portion of the earth formation when no core is being taken, which bit is releasably latched in the tool to be readily withdrawn on a wire line when it is desired to resume coring operations.

Another object of this invention is to provide a core drill of the character mentioned embodying novel and effectiv means for transmitting rotation or driving forces from the tool body to the plug bit.

A further object of this invention is to provide a core drill of the character mentioned in which the latch means for releasably retaining the core barrel and the valve for the relief of.

pressure in the core receiving barrel are embodied in a single compact unit.

The various objects and features of our invention will befully understood from the following larged fragmentary longitudinal detailed sectional view illustrating thelatch means for latching the plug bit and the core barrel in the body. Fig. 3 is a reduced horizontal detailed sectional view taken as indicated by line 33 on Fig. 2. Fig. 4 is an enlarged horizontal detailed sectional view taken as indicated by line 4-4 on Fig. 1. Fig. 5 is an enlarged, fragmentary, longitudinal detailed sectional view of the lower portion of the .tool illustrating the plug bit and the means for transmitting the driving forces from the body.

to the plug bit and Fig. 6 is a view similar to Fig. 5 showing the lower portion of the core receiving barrel seated in the cutter head.

The present invention may be said to comprise, generally, an outer barrel or body iii having a cutting head II on its lower end, a bit if to be lowered into the body it to act on the formation at the central or innerportion of the well bore, means It for latching or retaining the bit If in the body Ill, adapted to be released to permit withdrawal of,the bit If, means ll for transmiting turning forces from the body ID to the bit I! and a core receiving barrel i5 adapted to be lowered into the body Ill and latched in the core receiving position by the means I3.

The outer barrel or body it is adapted to be secured to the lower end of a well drilling string S of rotary drill pipe. The body I0 is a tubular structure or assembly including a drill collar ii. The drill collar II is an elongate member having a central longitudinal opening I! of substantial diameter. It is preferred to construct the drill collar IS with heavy or thick walls so that the drill collar imposes the desiredweight on the cutting means and lends-stability to the tool. A connecting member or sub i8 is provided on the upper end of the drill collar ii to facilitate the connection of the body it with the string S. The

e the lower end of the pin 20 forms a downwardly facing shoulder 22 at the upper end of the groove 2|. A sub or tubular member 23 is threadedly secured to the lowerrend of the drill collar IS. The member 23 preferably has a thick or heavy side wall and the lower portion of its opening 2! is enlarged or flared. The member 23 is provided with elements of the driving means If, as will be later described.

The cutting head ii is secured to the sub 23 on the lower end of the body iii and is operable to make an annular cut in the earth formation to form the main outer portion of the well bore.

The character or type of the cutting head It employed of course depends-uponrthe kind or earth formation encounterediifiln the case illustrated the head v tijis intended for use in soft earth formations and has are; "type cutting elements. It is to be understood y-that the core drill of the present invention mayiybe provided with a cutting head having toothed" rollers for use in rock or hard earth formations.

The head II has a threaded socket 25 in its upper end receiving a threaded lower pin portion of the tubular member. A central vertical opening 26 is provided in the head it to receive or pass the core. The cutting elements ,or blades 21 project downwardly and outwardly from the head to cut the well bore to the desired gauge and to trim or form the core. The cutting head it is provided with means for handling or direct-' ing the circulation fluid. A space 28 occurs in the head at the lower end of the member 23 and receives the circulation fluid from the opening 24. Circumferentially spaced ports 29 extend downwardly through the head it from the space iii to the lower end of the head to discharge the circulation fluid adjacent the cutting blades iii. In the preferred construction the cutting head it is formed to support or receive the bit it and the lower portion of the barrel iii. A. central cylindrical socket 3d is formed at the upper end of the opening it to receive parts of the bit 62 and barrel iii. The mouth of the socket 33 is flared to guide the parts into the socket.

The bit it is operable to cut away the inner or central portion of earth formation left by the blades 2? of the cutting head ii. In accordance with the invention the bit i2 is adapted to be lowered through the string S and body ill to its operative position at the head it and is adapted to be Withdrawn upwardly through the body and string when it is desired to install the barrel iii to obtain a core. The bit it includes a stem or body 3i and a head 32 on the lower end of the body 3!. The body :ii is an elongate member proportioned to readily pass down. through the drilling string and the body to to be received in the opening 25 with substantial clearance leaving an annular space for the circulation fluid. The body 3! is provided at its lower end with a threaded pin 33 and a downwardly lac an nular shoulder 34 at the upper end of the pin. The lower portion 0! the body 3! is adapted to be received in the socket in and the shoulder 35 is adapted to bear or rest on the bottom wall of the socket 30. The body 3| fits the socket 313 with slight clearance to readily enter the socket when the bit I2 is lowered into place.

The cutting head 32 is threaded on the pin 33 and projects downwardly in the opening 28 of the outer cutting head It assumingthe bit I! to be in its operative position The opening 26 and the upper portion or the head 32 maybe tapered. The cutting head I! is adapted to project downwardly beyond thelowerfaceoi the head II and its projecting lower end is prbvided with suitable cutting blades 35. A central pening 36 extends upwardly through the body It from the lower end of its pin 33 andjlateral ports fl connect the upper portion of the opening J36. with the opening 24 in the member 23. The cutting head 32 has a central cavity 38 and ports I! extend downwardly from the cavity to discharge the circulation fluid adjacent the cutting blades 35. The cutting head I2 is operable to drill away or break up the portion of the earth formation within the have a threaded connection with the upper, end of the bit body "to extend upwardly throudh the body Ill. The barrel section 4| may forms part of or may be of the same construction asm portion of the core receiving barrel is. The means it serves to latch or retain th'liit I! in its operative position in the tool during the usual drilling operations and serves to latdh the barrel I! in the body It! when a core is being taken. latch means or retaining means l3 includes an element arranged at the upper end of the drill collar is and a unit or latch means adapted to be secured to the upper end of thebarrel section M of the bit I2 or of the barrel H5. The elerneitt of the latch means l3 carried by the body m is in the nature of a latch ring 42 arranged tin the groove M. The ring 42 may be turnably or rotatably seated in the groove 2i and is new against vertical movement or displacement by the shoulder 22 and the lower wall of the groove.

The socket it and the pin 20 threaded together to connect the sub to with the drill collar in are such that they cannot be tightened down. m bring the shoulder 22 against the upper end all the latch ring 32. The ring 32 is proportioned to project into the opening ll of the drill collar it and the internal surface of the ring t? slopes downwardly and inwardly. The lower end of the latch ring 522 is preferably pitched and slopes downwardly and inwardly.

The latch means or retaining means it further includes a stem or latch carrier as adapted to be secured to the upper end of the section ll of the bit 62 and adapted to be secured tothe upper end of the core receiving barrel l5. s The carrier is an elongate element and is preferably integral.

In the preferred construction illustrated the lowor portion of the carrier th is removably threaded in the upper end of the section ti. A vertical opening at extends upwardly into the can id and has counication with the interior or the section til. Lateral ports 55 in thecarrim' it?! place the upper end of the opening at in com-- munication with the body opening it. A valve seat dd is held in the opening M by a threaded nut or retainer 67 and a ball valve 48 engages downwardly against the seat A6. The ball 52 is adapted to seal against the seat to to prevent the downwardly flowing circulation fluid from entering the barrel section 45. when the carrim' 43 is applied to the bit 82 or the section 4| on bit I2 the valve I is not essential.

The carrier 0 is reduced in cross sectionfl area and is shaped to have a plurality of circum ferentially spaced tongues 49. The tongues-I are located above the ports 45. Latches 50 m spaced about the reduced portion of the carrier 43 and have yokes 5| receiving the tongues B.

Pivot pins 52 are arranged in substantially hold-'- zontal openings in the togues 4B and the you II to pivotally support the latches 50. :The latches II project upwardly and outwardly anfl are formedv for latching engagement with the latches may be readily retracted by the socket or retrieving tool 63 as will later be described and so that the latches are readily received in the extending upwardly from the shoulder 50. The

shoulders 5d are engageable with the lower end path of the blades 31. A barrel section ti may of the latch ring 42 and the surfaces 55 are en- In accordance with the invention the circulation fluid from the latches.

gageable with the sloping interiorof the ring 42 when the latches are in their operative positions. The engagement of the shoulders 54 with the lower end of the ring 42 of course prevents upward movement of the carrier 43 and the parts connected therewith. The engagement of the surfaces 55 with the interior of the ring 42 limits the outward movement or pivoting of the latches 50.

. Means are provided for yieldingly urging the latches 50 outwardly to have automatic or latching engagement with the ring 42. Sets of leaf springs are arranged against the carrier 43 and curve downwardly and outwardly to bear against the inner sides of the latches 50. Blocks 55 are arranged against the upper portions of the spring I55 to assist in securing the springs to the carrier 43. The blocks 56 may be welded or otherwise fixed to the carrier 43. Dowels 51 cooperate with openings in the springs 55 and the blocks 55 to assist in connecting the springs and blocks. Grooves 58 are provided in the lower sides of the blocks 56 and are adapted to receive the upper end portions of the latches 5D.

The grooves 58 assist in guiding the latches 50 and serve to stabilize the latches. The upper sidesof the blocks 56 slope downwardly and outwardly to divert the downwardly flowing fluid from the latches 50. It will be seen that the blocks 56 assist in securing the springs 55 to the carrier 43, guide the latches 50 and divert the Means are provided for limiting the outward pivoting of the latches 50 so that the latches cannot assume positions where they may engage in obstructions in the drilling string S. The upper ends of the tongues 49 are provided with projections 60 and pins or lugs 6| are provided on the latches 50 to cooperate with the projections 50. The lugs 6| may be formed integral with the latches 50 or may be welded or otherwise secured to the latches. The projections 50 and the lugs 6| are related so that they prevent excessive outward pivoting of the latches 50 under the influence of the springs 55.

The latch carrier 43 is provided with a stem 52 engageable by a retrieving tool 63. The stem 52 projects from the upper end of the carrier 43 and has an enlarged head on its upper end engageable by spring urged gripping fingers 64 of the tool 63. The tool 53 includes a tubular sleeve 65 that projects downwardly around the fingers 64. The sleeve is cooper-able with the sloping upper ends. of the latches 50 and this cooperation serves to retract the latches 50 from the ring 42. The sloping internal surface of the ring 42 may serve to guide the lower end of the sleeve 65 into engagement with the sloping upper ends 53 of the latches 50. when the tool 53 is lowered to retrieve the bit l2 the sleeve 55 comes into contact with the latches 50 to retract the same and the fingers 64 then engage under the enlarged head of the stem 62 to grip the same. The tool 53 is suitably secured to the lower end of a cable or wire line L and upon being withdrawn from the well carries with it the bit |2 or the other means connected with the latch carrier 43.

The means I4 is operable to transmit driving forces or rotation from the body In to the bit |2 during the rotary drilling operations. The means l4 includes a plurality of circumferentially spaced ribs 51 on the wall of the opening 24. The ribs 61 extend vertically or longitudinally and are preferably formed in the flared lower portion of the opening 24. The upper and lower ends of the ribs 61 taper or slope toward one another. The means |4 further includes one or more dogs 68 on the bit carrier 3|. In the structure illustrated there are two diametrically opposite slots 59 formed in the carrier 3| and a dog 63 mounted in each slot. The dogs 68 are pivoted at their lower ends on pins 10* and are adapted to project outwardly from the mouths of slots 58. The vertical sides of the dogs 68 are flat for cooperation with the ribs 51. The forward sides of the ribs 51, relative to the direction of rotation of the strings S, are vertical and parallel with the lines radial with respect to the central vertical axis of the tool to cooperate with the flat vertical sides of the dogs 68. The rear sides of the ribs 61 relative to the direction of rotation of the tool may be pitched relative to radial lines. The flat vertical sides of the dogs 58 are adapted to engage the side walls of the slots 69 for the direct transmission of forces from the dogs to the carrier 3|.

Means is provided for urging the pivoted dogs 68 outwardly to cooperate with the ribs 61. A substantially U-shaped spring III is arranged between thespaced dogs 68 and the upper parts of its arms are secured to the dogs as by rivets 1| The spring 10 normally urges the dogs outwardly to protrude from the slots 69 and is yieldable to permit retraction of the dogs. The projecting or projectable portions of the dogs 63 have inclined upper and lower surfaces 12 that may engage obstructions in the drilling string S. The engagement of the surfaces 12 with obstructions or restrictions in the drilling string results in camming or pivoting of the dogs so that the dogs are moved into the slots 69 against the action of the spring 10. Means are provided for limiting the outward pivoting of the dogs 59. Notches 13 are provided in the upper outer corners of the dogs 58 and stops 14 are provided in the slots 69 to be engaged by the notched upper portions of the dogs. The notches l3 cooperate with the stops 14 to normally hold or stop the dogs 68 in positions where they project from the mouths.

' of the slots 69 for cooperation with the ribs 51.

The ribs 61 on the rotating body |0 engage the dogs 68 for the transmission of torque or turning forces so that the bit |2 is made to turn with the body In.

The barrel I5 is provided to receive and retain the core of earth formation left by the annular outer cutting head The barrel I5 is adapted to be lowered through the string S into the body ID to a position where it may receive the core and following the coring operation is adapted to be removed or pulled from the string S by the line L and the tool 63. The means l3 described above may serve to releasably latch the barrel i5 in the body III for the coring operation. The barrel I5 is an elongate tubular member or assembly proportioned to be received in the openings l1 and 24 with substantial clearance to leave an annular passage for the circulation fluid.

The core receiving barrel l5 includes the section 4| which may be similar to the section 4| or may be the self same section 4| of the bit I2 described above. The S6Cti011 is provided at its upper end with the carrier 43 and the means l3 so that the means 13 serves to automatically latch or retain the barrel l5 in the core receiving position when the barrel is lowered into the body ID. A tubular adapter 15 is threaded on the lower end of the section 4| and takes the 4 e aata en a eor thebqd ii described abo e, t: amo t o c m t b cutie im1 ii "e'r lifcarriesf a'core trappin'g orlretainingimeans, ered'to'bringitssleeye 8 into contact with the T m rdan ewi I hebm deta pects-jot they; i ine n w afih a il t rr th inyention'thebarrel l'i may be provided with any 'latches "fro m' the 12;" Simultaneously with table or type of'corecatcherforretain j'othe release of the latches? ftheflhgersfN grip qrei' nt e densiim t b i us ia tm tmi'!!! ar em to tub, 1"inert perlItisjthredded on thelower end lift jth'e jbar'rel {l5} upward mdvement of bithe'afl e 1i, anuz ase oc s 11m i er: f hl f 1 ,et e' n* 1e j c to end; flhefsdhl'retll receives a ring llfprovided *free'the same and to thereafter support the core a'pluralityfof spaced vertical'slotslsi Core in the barrel. Thebarrel i isreadilyiemovcatchingdogs"I80 larejpivotallyi'moiintedin the'j able ontheflinelt bit I? may then be rejj s1ots is-and a urgeddownwardlyfindinwardly; turned-to its joperative' 'position 'in the body it bysprlngs-"ti The ring '-18may bewelded or fandthedrilling operations" may ibe' resumed. "otheifvfrise ihred intheso'cket' 11'.' Whentl 1e Havingdescribed'only-a typical preferred form rel Iii islowered into'the b'ody'the lower portio'n and fapplication of ourfintention'," wedo not wish [of thelmemberlt'enters the socket 30 of thecut to beor restricte'd'td the 'speciil'cjfdetails flung-"head; I i and its'lower end mayres'ton the bottom 'wall' 'of'the socket to'support thebarrel. F "any variations or modifications that may "appear The member lt isproportionedto' enter the sockto th s skilled intheart or fall withinthe scope f"""et-;30 with'slight clearanceso'thatthe-barrel I5 of thefollowingclaims:

may remainnomrotatable during the drilling'op- Having described our invention, we claim:

" "era'tion. With the member li entered in the 1. A-c'oredrill for'use ona tubular rotary well socket 311 the core received by the opening 28 is drilling string comprisinga tubular'body for atadapted to enter the lowerendof the barrel l5. taehn'ient' to the string, a tubular cutting head I The pivoted dogs 80 are operable to bite into and on the lower end of the body. a barrel to be lowsupport the core whenthe barrel I5 is raised at ered through the string into the body to receive the termination of thecoring operation. the core formed by the cutting head, a bit to be I In the use or operation oi! the tool of this inlowered through the string into the body when ,vention the body I0 is connected with the lower the barrel is not in use and operable to drill away 'end of the rotary well drilling string S and the 30 the core, means at the head for supporting the string is rotated so that the cutting head ll acts a lower ends of the .barrel and bit, position means on the formation at the bottom of the well bore.- for transmitting rotation from the body to the During the usual drilling operations the bit I! is bit comprising an internal rib in the body adpositioned in the body It to drill away the cen- Jacent the head having a radial forward face and tral portionof the bore. As above described, the a pitched rear'face, and a yieldable dog on the hatches 50 cooperate with the under side of the bit cooperable with'the rib; a latch ring rotatring' 42 to hold the bit l2 against upward move- 7 ably supported in the body,ta-carrierattachable ment relativeto the body l0 and the latches thus to the upper end of the barrel an'dthe' upper end retain the bit in its operative cutting position. of the bit, and'spring urgedlatches on the car- The'dogs 68 are engaged by the ribs 6! so that rler for engaging the ring to hold the barrel and the rotary forces are transmitted from the body 1. the bit in their operative positions in the body.

- ill to the bit l2. Circulation fluid is pumped" 1 2. In acoredrill for-use on atubular well drill- "downwardly through thespringS to flow through ingstring, a tubular body to be secured to the the body In and discharge from theports 29 to lower :end of the string, the body including the cutting" head ll. Circulation fluid passes 4 threadedly connected sections, a ringretained bethrough the ports 31 and the slots '68 to flow tween said sections to be held'against vertical through the opening and discharge from the movement and adapted to freely rotate, the ring ports 39 01 .t b t z,- projecting. inwardly atthe interiorof the body,

- 1: When it'is desired to obtain acorethetool 63 a cutting head at ".thelower endvoi the body for is run down'through thestring S on the line L: making an annular cut'in the earth formation,

to enter the upper end of theibodyill; r The'tool a, a barrel: to be: lowered-through the string into 63zis=lowered until-its.sleeve fiiizcooperates with: 2 the body-to :receive the core left by the cutting theinclinediupper ends iiofthe latches .50 to re-- rheadjmeans at thezheadfori rotatably supporting tract the latches'from thelatchringlZ; Simul-i s'thefbarreLacarrierzon the; upperlend of-the bar- ;taneously with, this retraction of thelatches iii,-'*55 rel,ivalvermeansin the'rcarr'ienfor relieving inthe fingers- 64: come into;-;gripping engagement; ternal, pressure :from the barrel, and-spring urged with ,theenlargedend-ot the stenr 62 sothat the latches on .theicarrier ,tor'engaging-under the ring itookobtam tflrm h ld f thehstem. II'he line a releasably hold. the barrel inthercore, receiv- L is thenraisedito withdraw? the bit l2 and then; ,iingspositioneinethe body. 21;5. lparts-associated therewithawfrom the -body liii'al a; 3. 1m au'core 'dri1l ion-use ton, tubular well .irhegbarrel -il. provided at its upper end with the drillingstrine. a tubularbody 1 1041 8 Secured to the carrier- :43: 'andi'the ,parts thereon is then lower .end ,of the'strinsithebody including threaddown 'through thelstrina's to: itszposition in the -.edly connected; sections; atfreely rotatable ring "bodylz.lilrzli-Thezlmember l6 ofizthe i barrel l5 re ned b ween saidsections to be held against adapted toseatin-the socketflil when the harmless; vertical movementandzto pljoie efir h i r l5 reaches the position where the latches 50 005' of the-body,a cutting head at the lower end of operateuwith theqringeylli, The spring urged= h both/ iar making anannular-cut-in the earth clined innerrsurfac :ofthering 4 2, and are res ring into the body to receive the. core-left by tractedl by this engagementiintil-theirshouldersI 101 118 cutti hfifli: means :at the head for rotatilglatch underthe ring.-; ='l'h i s Jatchesthe barrel eablyslipportingthe barrel,acarrier onthe upper alfiqi'n the body: Ill and, the ebarrel is ready for end ofthe barreL yalve means in thecarrier for 1 e 'the coring operation. Thecorevdrillisoperated inz-the lusual mannerto'cuta core and the core xii -urged latches on themarrierl-forengaging under isvreceived in, the'barrel 15. :When asuflicient the ring to. h ld e barre n e 9 y,- a S m "-her ein set forth, but wishtd reserve to ourselves latches: 50 vcome:into:e 'igagement with, the int-,2, fonnation, -a bartebtobelowered:through the relievinginternal pressure fi om the, barrel, spring on the carrier engageable by a retrieving tool for removing the barrel, and sloping faces on the latches engageable by the retrieving tool to release the latches.

4. In a core drill for use on a tubular well drilling string, a tubular body to be secured to the lower end of the string, an annular cutting head on the lower end of the body, an internal shoulder on the body spaced above the cutting head, an, internal rib on the body above the cutting head, bit means adapted to be lowered through the string into the body to drill away the core of formation left by the cutting head, releasable latch means on the bit means for engaging the shoulder to hold the bit means in active position, and a retractable spring held dog on the bit means engageable with the rib for the transmission of rotation from the body to the bit means.

5. In a core drill for use on a tubular well drilling string, a tubular body to be secured to the lower end of the string, an annular cutting head on the lower end of the body, an internal shoulder on the body spaced above the cutting head, an internal rib on the body above the cuting head, bit means adapted to be lowered through the string into the body to drill away the core of formation left by the cutting head, latches at the upper end of the bit means engageable with the shoulder to hold the bit'means against upward movement in the body, and a spring held dog on the bit means below the latches adapted to retract upon movement through the shoulder and cooperable with therib for the transmission of rotation from the body to the bit means.

6. In a core drill for use on a tubular well drilling string, a tubular body to be secured to the lower end of the string, an annular cutting head on the lower end of the body, a latch ring in the body spaced above the cutting head, spaced longitudinal ribs on the interior of the'body adjacent the cutting head, a bit adapted to be-lowered through the string and body to the head to drill away the core of earth formation left by the head, a structure extending upwardly from the bit, pivoted spring urged dogs on said structure retractable through contact with the latch ring and other restrictions in the string and body and cooperable with the latch ring for the transmission of rotation from the body to the bit, a carrier at the upper end of said structure, and pivoted latches on the carrier engageable under the latch ring to releasably retain the bit and said structure in the body.

gitudinal ribs on the interior of the body adjacent the cutting head, a bit adapted to be lowered through the string and body to the head to drill away the core of earth formation left by' and cooperable wih the latch ring for the transmission of rotation from the body to the bit, a

' carrier at the upper end of said structure, a

stem on the carrier engageable by a retrieving tool for removing the bit and structure from the body, and pivoted spring held latcheson the carrier for engaging under the latch ring to retain the bit and said structure in the body, and latches having sloping faces engageabie by said tool to cause retraction of the latches.

8. In a core drill for use on a tubular well drilling string, a tubular body to be secured to the lower end of the string, the body including threadedly connected sections, a ring retained between said sections for free unrestrained rotation and to project at the interior of the body, a cutting head at the lower end of the body for making an annular cut in the earth formation, a barrel to be lowered through the string into the body to receive the core left bythe cutting head, means at the head for rotatably supporting the barrel, a carrier on the upper. end of the barrel, valve means in the carrier for relieving internal pressure from the barrel, spring urged latches on the carrier for engaging under the rotatable ring to hold the barrel in the core receiving position, and parts on the carrier guiding the latches and diverting the fluid from the latches, the latches having surfaces clear of the ring and said'parts engageable to release the latches from the ring.

9. A core drill for use on a tubular rotary well drilling string comprising a tubular body for attachment to the string, a tubular cutting head on the lower end of the body, a barrel to be lowered through the string into the body to receive the core formed by the cutting head, a ring supported in the body for free unrestrained turning, and positively held against vertical movement relative to the body, the ring being spaced above the head, means at the head for supporting the lower end of the be reLLa', carrier secured to the '1'. In a core drill for use on a tubular well drilling'fstring, a tubular body to be secured to the lower end of the string, an annular cutting head on the lower end of the body, a latch ring in the body spaced above the cutting head, spaced ionupper end of the el, and a spring urged latch on thecarrierngageable with the ring to hold the barrelagainst upward movement in the body, the latch having a surface in the interior of the ring clear of the ring and engageable by a retrieving tool to release the latch from the ring.

ALFRED c. CATLAND. PHILIP dm'aoMsoN.

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