US2596832A - Core barrel - Google Patents

Description

May 13, 1952 E. B. WILLIAMS, JR

CORE BARREL 3 Sheets-Sheet 1 Filed Marh 7, 1949 wwmfww w wmwwm d O L l ma u Ht .H m 3. w q N, .0 a a n W 71% w wum wwwwi l L mi@ .I w l I l |||..I|.||H Il 1I S, WN\\\\\\\% LZ a 0 Wmnw Arron/vers May 13, 1952 Filed March 7, 1949 E. B. WILLIAMS, JR

CORE BARREL.

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May 13, 1952 E. B. mLuAfMs, JR 2,596,832

CORE BARREL 5 Sheets-Sheet 5 Filed March '7. 1949 gig. .9. l/ q INVENTO? my/M@ ATTORNEYS Patented May 13, 1952 UNITED STATES .PATENT @FFE-CE .Edward B. Williams, Jr., Greenville, Tex.

`Application*March 7, 1949, Serial-No. 79,988

`10 Claims. l

This invention relates to :core lbarrels .such as used in coredrilling of :earth formations -..to determine the vrock structure .and .has .for its principal objectstoprovide acorebarrelin which the core hasfreepassage intothe receivingbarrel during .drilling operations; .to provide .a .core .barrel with Lmechanism that .is 4responsive to pressure of `the drilling uidfor supporting the core-receivingbarrell and. preventing engagement of the core gripping .mechanism :with .the ..cQre; to provide :.a corebarrelawith core gripping; mech- .anism .adapted to function automatically in gripping the core .upondropping ofthe Ac orereceivingv b arrelwhenthe .numnpreSSll-Iei .iS .shutoff prior to adding sections .of drill pipe or pulling the drilling string from the borehole; and to provide the core barrel With'asimple mechanism for Vmaintaining pressure of the drilling fluid whichis required in supporting Vthe coregreceiving barrel in position-to prevent engagement of j the-coregripping mechanism upon fluctuatonsin the drilling fluidgpressures.

In accomplishing these vand 4other objects of the invention ashereinafter .pointed out, lhave provided improved structure, the `preferred form r of which isillustrated in they accompanying drawing wherein:

Fig. lis an elevational '-.view of the lower end of a drilling string .equipped .with a core barrel and operating mechanism .embodying the .fealtures of A,the presentinvention, parts being .bro-Ken away and .shownin section toshowinterior construction. y

Fig. 2 is an enlarged ".longitu'dinal `section through the lower portion ofthe core barrel, particularly illustrating connection o-f the drill bit and themounting ofthe core gripping mechanism.

Fig. 3 isa similar vsectionlthrough the upper portion of the core .barrel .and the mechanism associated therewith to .retain the coregripping mechanism .out of contact with v the core andto permit ,automatic engagement of the core gripping mechanism responsive to thegpresence and absence of pump ypressure on thexrilling fluid, respectively.

Fig. 4is-a .section through the drilling string near the connection of 'the 'drillpipa` particularly illustrating. reieaseofthepstonvalve controlling theports for bleeding thedrillingfluid from the drillpipe'priorto Vpullingof the drilling string as when removingthe corejfrom thebore hole.

Fig. '5 isan enlargedsection through'the lower end ofiithecore barrel and drill bit` particularly ,f illustrating the 'core gripping `or catching :mechanism.

Fig. .6 is van enlarged .section .through the .bleeder valveshowing .the .Valve .piston in lpositionforclosing the ports .through Whchdrilling fluidisreleasedfromthe drillpipe.

.Eig. 71s. a,horizontal.,s ection through the drill bit and .core catcher taken on the line 'I-;'I of Fig. 8 is a horizontal section through the inner and outer core b arrelsonthe line 8-8 of Fig. 2-

Fig. 9 is anenlarged section on the line 9-9 of Fig. 3, particularly illustrating the choke ports. l

Fig. 10 is an enlarged horizontal section through the controlpiston on the line IIl-IIJ of Fig.

Fig. 11 is a similarhorizontal section on the line I I-II of Fig. 3, particularly illustrating the ernbodyingthe features of the present invention,

the corebarrel beingconnected with thedrilling string through .a screen housing `tube 3 and a bleeder. coupling. 4.

.The core'barrel assembly 2 includes an outer barrel .5 "havingitslower end terminating in an externally threaded y.tool joint 6 which engages .in the' internally Vthreaded neck'l of acore bit 8. l'lfhacore'bitgtmay comprise a cylindrical body 9 'havingaflower circumferential drilling face I0 `35 encircling. an axial. core passageway I I uthrough Whichlthe core'fee'ds-through -core Vcatcher I2 Yand Vinto the 'inner or core Vreceiving barrel I3.

Above the entrance tothe icore bi'tthe vpassageway ',II "flares "outwardly as at vI-i to provide a wedging surfacetfor seating -and contracting the corejcatcher I-2'- whenthe corecatcher-moves into engagement 'therewith as-later described, Above Vthe-annular fiaring seat I4, the passageway'is Lprovi'ded'.withvafshoulder I5 terminating in a Ycy'flindrical fbore |15 -in v'which is seated la liner II ,having -cii'cumferentially spaced-vertical ribs vI3 forming :vertical lpassageways or watercourses vI9 therebetweenfiori-theflowl of drilling fluid around Vthecore for Vwashing cuttings'made' by the bit upwardly within the bore hole.

The inner barrel Y I3 is' Y of smaller Ydiameter than thei innen diameter oftheouter barrel to providefa--vertical longitudinalipassageway 2| .for downward flow of `'drilling ffluid fto lthe Water.- rcourses IS. The linside'fdiameterof 'the v.inner barrel is of such size and character as to permit free feeding of the core therein. The lower end of the inner barrel is externally threaded as at 22 (Fig. 5) to mount the core catcher I2 which includes a collar 23 vertically guided by the ribs I8 to retain concentric alignment of the inner barrel. Fixed to and depending from the collar is a ring of arcuate segments 24 that are formed of thin flexible material and which carry a plurality of gripping ngers 25. The gripping fingers have a substantially hard granular material coating the inner faces thereof as indicated at 26 so as to frictionally engage the core when the iingers are contracted about the core byv wedging action of the seat I4 on the taperedr exterior faces 21 ofthe respective lingers as theV barrel moves downwardly responsive to shutting oli the pump pressure as later described.

To facilitate assembly, the outer barrel comprises a lower section 28 and an upper section 29 connected by a threaded joint 36 as shown in Fig. 2. The upper end of the upper section 29 has a closed head 3I having the outer circumference of reduced diameter and externally threaded as at 32 to mount the coupling joint 33 in which the control piston and choke mechanism is slidably mounted as later described. The head 3| is provided with an axial bore 36 which reciprocably mounts a tubular rod 31 having its lower end 38 journalled within a swivel head 39 that is contained within theupper end of the outer barrel and which is threadedly connected as `at 40 with the upper end of thel inner barrel I3, the swivel head having an axial bore 4I in which is formed oppositely facing annular shoulders 42 and 43 seating antifriction bearings 44 and 45, the bearings being retained against the shoulders by sealing rings 46 and 41, the lower ring 41 being retained against a shoulder 48 on the lower end of the piston rod' by a nut 49 that is threaded onto the reduced threaded extension 50 thereof as clearly shown in Fig. 3. The upper sealing disk is retained by jamb nuts 5I and 52 that are threaded onto the piston rod to cooperate with the lower nut 49 vin rotatably anchoring the piston rod 31 from longitudinal movement relatively to the inner core receiving barrel I3. With this arrangement it is obvious that the piston'rod 31 may rotate* freely within the inner barrel I3 while supporting the inner barrel with the gripping ngers 25 of the core catcher I2 out of wedging engagement with the seat I4. The piston rod 31 has a plurality of liquid seals 53 to seal the axial bore 36 and retard leakage therethrough of the drilling nuid so that the supply of drilling iiuid is diverted into the annular passageway 2| through a plurality of ports 54 that are arranged in circular series about the piston rod 31 as shown in Figs. 3 and 9. As above stated, the piston rod 31 is hollow to provide a vertical passageway 55 therethrough for relieving iiuid within the inner barrel as the core rises therein during drilling oprations. Thejoint 33 has a coaxial cylindrical bore 56 in the mid portion thereof to form a piston chamber in which is slidably mounted a piston 51 that is connected with the upper end of the piston rod by threading of the terminal end of the rod into an internally threaded socket 58 of the piston (Fig. 3).

I'he entrance of the piston chamber 56 flares' 3l to house a choke' mechanism 62 by which (a substantially uniform pressure is maintained on the drilling fluid passing through the ports 54 from above the piston as later described. The choke mechanism includes a collar 63 that is threaded on the piston rod in abutting engagement with an annular shoulder 64. Carried by the collar 63 and projecting outwardly and circuinferentially thereof is a ange 65 that is adapted to reciprocate with the piston rod within the counterbore 60 but which provides an annular space 58 therebetween to pass the drilling fluid.

Mounted in the flange in axial alignment with fiow'through the ports 54 is controlled by position of the choke pins relative to the choke orifices 68 in the members 68 so that substantially uniform pumping pressure can be maintained on the drilling fluid in the passageway 2l. The piston 51 has an axial threaded bore 69 mounting a nipple 10 (Fig. 3) that reciprocates with the piston through a sleeve L1I that is threaded within an internally threaded bore 12 of the joint member 33. the sleeve carrying sealing rings 13 and 'i4 for forming liquid seals about the nipple. The upper end of the joint 33 has an internally threaded socket 15 for receiving an externally threaded pin 16 on the screen housing section 3. Fixed to the upper end of the sleeve 1I is a tube '11 carrying a screen section 18 by which the drilling fluidis screened while ilowing from the bore of the drill pipe I to the nipple 10. The upper end of the tube 11 'is closed as at 19 and the tube is centered within the bore ofthe housing by radially extending wings 8 I. Formed in the piston in connection with the lower end of the iiow tube 1I] are a plurality of radial channels 82 that connect with'vertical channels 83 so that the drilling iluid is adapted to be passed through the piston and to act on the underside thereof in retaining the piston in its uppermost position to suspend the inner barrel I3 with the gripping iingers 25 of the core catcher in the upper portion of the flaring seat I4. The fluid relief passageway through the piston rod connects with a radial port 84 that leads to a vertical port 85 opening through the top of the piston and which discharges through the piston chamber to the exterior of the joint `33 througha lateral port 86.

In order to maintain pressure within the bore 4I of the swivel head and prevent the possibility of leakage of drilling fluid through the ring seals into the bearings, the swivel head is provided with a pressure tting 81 by which lubricant is admitted under pressure to ll the space within and between the bearings. To maintain the pressure on the lubricant, a ram 88 is slidably mounted within a lateral bore 89 and which is actuated by a piston SII)v that is slidable in a counterbore 9| to project the ram into the lubricant chamber responsive to pressure of the drilling fluid actingon the external siderof the piston.

When pulling the drilling string, it is desirable to bleed the drilling fluid from the drill pipe and this is accomplished by providing the bleeder 4. The bleeder` 4 comprises a drill pipe joint 92 having a pin end 93 threaded into the internally threaded socket 94 provided in the upper end of the screen housing section 3. The upper end of the coupling 92 has Van Vinternally threaded socket '95 for receiving the pin end 96 ofthe lower joint of drill .pipe I. Formed inthe cou' pling member 92 is a coaxial rpistonchamber '91 slidably mounting a `piston kvalve i98-which is adapted to cover and uncover lateral ports99 openingthrough the sides ofthe-coupling memberas best shown in Fig. 4. The piston 98 is provided with suitablersealing rings |00 to prevent leakage of drilling fluid therearound and the lower end is tapered asindicated at IOI toengage aring-shaped seat |02 that is fixed inthe lower end of the pin 93. The valve piston 98 vhas an axial port |03 terminating at theupper fis retained in an upper position within the piston cylinder to normally cover the ports'99by means of a shear pin IIO that is inserted throughJan opening III and which is-retained'by a;plug I|2 threaded into a counterbore II3 of the.v opening. The pin when in position engages in an annular groove II4 of the pistonl and supports the piston in-fcovering relation with the lateral ports 99 `so that drilling fluid passing downwardly through the drill pipe is conducted through the pistonand checkvalve |06 and strainer section I8 to the core barrel.

When it is desired to ybleed thedrilling fluid from the drill pipe, the-shear pin'I I0 is broken by means of a sinkerbar'l I5 that is dropped through the drill pipe from the top of the drilling string, the sinker bar being provided `with a `pointed terminal IIB which is radapted to freadily `pass through the port |03 of the pistonand Aguide-a tapered shoulder II1 cn the sinker-barinto contact with the seat |04 with sufficient force to eifect shearing of thepin IIO and vcause downward'movement of the piston 98 so as to'uncover the bleed ports "99. The drilling fluid maythen bleed through the yports '99'into theboreholeas vthe drill pipe is pulled therefrom.

In order to prevent turning of the choke pin carrier collar65, the collar is'provided'with depending pins I I8V thatare slidable in guidebores I I9in thehead 3I-'(-Fig. 12).

In using the core barrel, the sections 12, 33, 3 and 4-are connectedtogether as shown'in Fig.'1 and are lowered into the bore hole-"for connectionwith the first joint ofdrill pipe I. The core drill is progressively lowered into the bore hole upon connection yof vadditional joints of Adrill pipe as infconventional p ractice untilthe core bit reaches the bottom of-fthe bore hole. Since there is vno pump pressuresupon-running thedrilling string into the Ybore hole, the `inner barrel I3, swivel head 39,choke' mechanism 162, piston 51, and nipple I0 are in their -lowermostposition with the grippingfingers Y25 of the core'catcher y wedging in theflaring gseat I4.

vUpon starting drilling operation,-drillingjuid is supplied under pump pressure-through the drillfpipeso as to'effect circulation4 for bringing cuttings made byl thebit to theltop-cf -theground The Vdrilling fluid "flows `throughth'e f screen 58, pipe TI, nipple IIIypiston ports 82 Vand'03 into the lower end ofthe :piston chamber 56. Since the choke pinsv 66 are'practicallyfclosing the ports of the choke membersowand thepressurev above the'piston is equal to :the "lesser pressure of the 'upiiow .around the drill pipe, vthe '-higherpressure acts-underthe piston-'51'#to'raisethe-pistonunits vings 44 and 45.

cylinder andlift the inner core .receiving barrel I3. through the connecting rod3'l and swivel head connection 39. As long as pumpgpressure. is admitted into the drill pipe, the inner core receiving barrel will remain in its uppermost position. This'is obvious because should the inner barrel tend to drop under-a reduction inpump pressure, the iiow would' be restricted through the orifice members which acts to increase the pressure below the piston sufficiently to lift and vretain the Vpiston in position to unseat the fingers of the core catcher from thetapered seat I4. In this'position the coreresulting from rotation ofthe drill bitisffree to-feed upwardly withinthe corexreceiving barrel I3 iwithout -wedging or'breaking of segments through dragging .of the catcher Von the core.

When the drill pipe is-rotated,`the outer barrel 2 rotates with'the drill bit 8, however, .the inner barrel may remain stationary since 'the swivel head-thereof isfree to rotate onthe antifriction bearings 44 and145. Therefore,the innerbarrel will notvrotate while the core.' is feeding. thereinto incidental to progress made by the drill bit.

When it is necessary toshut down .drilling operations aswhen pulling the drilling string, the pump pressure is shut off from .the vdrill pipe whereupon pressure .equalizes ,aboveand below Vthe piston. 51 to allow. settling of the .corereceiving barrel so that the ,wedgefaces'l cooperate with the iiaring. seat I4 to effectmovementof the gripping faces'of .the core catcherinto gripping contact with the lower endof Lthe core then in the barrel. The core may thenbe broken off iby lifting and slightly rotating the drilling string, after whichthe drilling string is -withdrawn from the' well carrying the core `therewith. Y

In pulling the vdrillingstringit maybe desirable tobleed .the drillingfluidfinto the bore hole. This is effected by dro-ppingthesinker bar through the drill pipe so as .toshear Yorf thepin III) retaining the piston 98 in position to close 'the ports S9. The piston 98 willthenshiftdownwardly sincetheipressure is equalized on the respective ends thereof and-uncover the ports 99. 'I'he liquid above the ypiston .is then drained through the ports 99. When the bit-is in drilling operation the drilling iiuid passesthrough the choke members around the `swivel head .and through the passageway .2| to the Sdrill bit so as to wash the cuttings upwardly around the outside of the core barrel. Pressure of the drillingfluid acts-on the piston so as to maintain pressure on the llubricant in the swivel head and thereby prevent the drilling fiuid from enteringthe bear- 'Ihe liquid vdisplaced. 'from the inner core barrel by feed of the core therein is displaced through thehollow connecting rod 3'I and through the ports 84 and 85 of the piston to be discharged throughfthe lateral port 86.

From the foregoing it is obvious that the core has free passage to the receiving barrel during drilling and ther core catcher catches orgrips the core only when the pump pressure is-shut-off at the upper end of the drilling string. 'The core catcher, being free of the core during drilling. operations does not tend tointerferewith entrance of the core or wedging of the core responsive to particles breaking -off andvwedging on the core catcher since the fingersof the core catcher are in adequately spaced relation-with the core during-normal-drilling operations. It isalso obvious entering mthe working barrel nwhereby substan f tially uniform. pressure is'maintained on thev lifting piston, howevenif the pump pressure is shut f 'down the drop in pressure under, the piston will immediately effect equalization of pressures on .the'respective sides thereof to permit dropping of the assembly so as to' automatically grip the core and assure complete removal thereof along with the core barrel. It isV also obvious that While the core is free during drilling, the core catcher may be engaged with'the core at any time by shutting oi the drilling iluid. The action of the core catcher is, therefore, under complete control of the driller and permits taking of substantially continuous core samples without loss of sections intermediate the cores that are removed.

What I claim and desire to secure by Letters Patent is:

Y l. A core barrelincluding outer and inner barrels. withthe innerbarrel being movable coaXially within the outer, barrel, a contractable core catcher. carried by the inner barrel, means carried by the outer barrel to effect contraction of the core catcher upon downward movement of the inner barrel within the outer barrel, means connected with the outer barrel for supplying a drilling. fluid under pump pressure, pressure actuateble means connecting the inner barrel with the outer barrel and responsive to pump pressure of the drilling fluid for supporting the inner barrel from said downward movement, and choke means carried within the outer barrel and movable with the inner barrel to maintain substantially uniform pump pressure of the drilling iiuid on said pressure actuatable means.

2. A core barrel including an outer barrel, a core bit fixed to the outer barrel and having an axial opening for passing'a core therethrough,

an inner barrel, means supporting the inner -barrel in concentric relation with theouter barrel and for axial movement relative to the outer barrel, a core catcher carried by the inner barrel and having means for gripping said core upon I axial movement of the inner barrel in one direction, means for supplying drilling fluid Linder pressure, pressure means responsive to said drilling fluid for axially shifting the inner barrel within the outer barrel in the opposite direction to effect release of the core catcher, and means responsive to fluctuations in said pressure ci the drilling fluid to maintain pressure of the drilling fluid substantially uniform on said pressure means. l

3. A core barrel including outer and inner barrels with the inner barrel being movable axially within the outer barrel, a cylinder member carried by the outer barrel and having a piston chamber therein, a piston slidable in the piston chamber, a rod connecting the piston with the inner barrel, means for supplying a drilling fluid to the piston chamber under pressure to move said piston in the cylinder and lift the inner barrel, said cylinder having a vent port at the end of the piston opposite to said high pressure for equalizing pressures on said piston upon shutting down the drilling fluid pressure, means for Venting the inner barrel through said vent port, a conn `tractable core catcher on the inner barrel, and core catcher contracting means on the outer barrel and adapted to be engaged by the contractable core catcher upon shutting down the pressure on the drilling luid.

4. A core barrel including outer and inner barrels with the inner barrel being movable axially Within the outer barrel, a cylinder mem- -ber carried by the outer barrel and having a piston' chamber therein, a pistonslidable in the piston chamber, a rod connecting the piston with the inner barrel, means for supplying a drilling fluid tothe piston chamber under pressure to move said piston in the cylinder and lift the inner barrel, a contractable core catcher on the inner barrel, a core catcher contracting means on the outer barrel and adapted to be engaged by the l contractable core catcher upon shutting down the pressure on the drilling fluid, an orice member carried by the outer cylinder for passing flow of drilling fluid, and a choke pin carried by the piston rod and movable into the orifice member upon fluctuations in the pump pressure to maintain substantially uniform pump pressure acting on saidpiston;

5. A core barrel including outer and inner barrels with the inner barrel being movable axially within the outer barrel, a cylinder` member carried by the outer barrel and having a piston cham Jer therein, a swivel head on the upper end of the inner barrel, a piston slidable in the piston chamber, a rod connected with the piston and rotatably connected with the swivel head, means for supplying a drilling iluid under pressure through said piston to move said piston in the cylinder and lift the inner barrel, a contractable core catcher on the inner barrel, a core catcher contracting means on the outer barrel and adapted to be engaged by the ccntractable core catcher upon shutting down the pressure on the drilling fluid, a choke orifice member carried by the outercylinder for passing ilow of drilling fluid, and a choke pin carried by the piston rod and movable into the choke orince member upon fluctuations in the pump pressure to maintain substantially uniform pump pressure acting on said piston. A

6. In'an apparatus of the character described, an outer barrel, a core drill bit fixed to the lower end of the outer barrel and Yhaving a core catcher engaging seat, a coupling member connected with the upper end of the core barrel and having a piston chamber, a piston in said chamber, a connecting rod depending from the piston into the outer barrel, a swivel head rotatably mounted on the depending end ofl the connecting rod, an inner barrel carried by the swivel head, a core catcher on the lower end of the inner barrel and having gripping means adapted to engage said seat upon downward movement of the piston in sov Vmembers carried .bythe outer barrel in cooperation with the choke for passing drilling fluid from below the piston to the drill bit in volume depending upon the position of the choke pins in said orifice members.

7. In an apparatus of the character described, an outer barrel, a core drill bit xed to the lower end of the outer'rbarrel and having a core catcher engaging seat, a coupling member connected with theupper end of the core barrel and having a piston chamber, a piston in said chamber, a connecting rod depending from the piston into the outer barrel, 'a swivel'head rotatably mounted on the depending end of the connecting rod, an

innerbarrelcarrie'd by the swivelhead, a coreV catcher on the lower end of the inner barrel and having gripping means adapted to engage said seat upon downward movement of the piston in said cylinder, a nipple connected with the piston and having sliding movement in the coupling member, said piston having ports connecting the nipple with the opposite end of the piston chamber on the rod end of the piston means for conducting drilling uid under pump pressure to said nipple to act on the rod connected end of the piston, a collar fixed to the connecting rod and having a plurality of choke pins, orifice members carried by the outer barrel in cooperation with the choke for passing drilling uid from below the piston to the drill bit in volume depending upon the position of the choke pins in said orifice members, and means for discharging drilling fluid from the inner barrel.

8.. In an apparatus of the character described, an outerbarrel, a core drill bit xed to the lower end of the outer barrel and having a .core catcher engaging seat, a coupling member connected with the upper end of the core barrel and having a piston chamber, a piston in said chamber, a

hollow connecting rod depending from the piston into the outer barrel, a swivel head rotatably mounted on the depending end of the connecting rod, an inner barrel carried by the swivel head, a core catcher on the lower end of the inner barrel and having gripping means adapted to engage said seat upon downward movement of the piston in said cylinder, a nipple connected with the piston and having sliding movement in the coupling member, said piston having ports connecting the nipple `with the opposite end of the piston chamber on the rod end of the piston means for conducting drilling fluid under pump pressure to said nipple to act on the rod connected end of the piston, a collar fixed to the connecting rod and having a plurality of choke pins, orifice members carried by theouter barrel in cooperation with the choke for passing drilling fluid from below the piston to the drill bit in volume depending upon the position of the choke pins in said orice members, said piston having a port connecting the hollow rod with the piston chamber at the nipple connected end of the piston, and said piston chamber having a discharge port through a side of the coupling member.

9. An apparatus of the character described including a drill pipe for supplying a drilling uid under a pump pressure, an outer barrel, a core bit connected with the outer barrel, a core receiving barrel having axial movement within the outer barrel for receiving therein a core made by said bit, a core catcher connected with the core receiving barrel and having an operating engagement with a part carried by the outer barrel upon axial movement of the core receiving barrel within the outer barrel, means connecting the drill pipe with the outer barrel including means responsive to pressure of the drilling fluid and having operative connection with the core receiving barrel for controlling engagement and disengagement of the catcher with a core, and choke means connected with said actuating means to maintain substantially uniform pressure of the drilling fluid on said pressure responsive means when the drilling fluid is under pump pressure.

10. An apparatus of the character described including a drill pipe for supplying a drilling fluid under a pump pressure, an outer barrel, a core bit connected with the outer barrel, a core receiving barrel having axial movement within the outer barrel for receiving therein a core made by said bit, a core catcher connected with the core receiving barrel and having an operating engagement with a part carried -by the outer barrel upon axial movement of the core receiving barrel within the outer barrel, means connecting the drill pipe with the outer barrel including means responsive to pressure of the drilling fluid and having operative connection with the core receiving barrel for preventing engagement of the catcher with a core, and means in said connecting means responsive to any pressure fluctuations in the drilling uid pressure for maintaining a constantly uniform pressure of the drilling fluid on said fluid pressure responsive means as long as drilling iluid is being supplied through the drill pipe under pump pressure.

EDWARD B. WILLIAMS, J R.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,643,338 Halvorsen Sept. 27, 1927 2,128,914 Burke et a1. Sept. 6, 1938 2,381,844 Stokes Aug. 7, 1'94'5 2,490,512 Deely Dec. 6, 1949 2,532,716 Havlick Dec. 5, 1950

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