US2905439A

US2905439A - Means for drilling

Info

Publication number: US2905439A
Application number: US638652A
Authority: US
Inventors: Leo A Martini
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-02-06
Filing date: 1957-02-06
Publication date: 1959-09-22
Anticipated expiration: 1976-09-22

Description

SePt- 22, 1959 L. A. MARTINI 2,905,439

MEANS FOR DRILLING Filed Feb. e, 1957 2 sheets-sheet 1 A GENT sept. 22, 1959 Filed Feb. 6, 1957 L. A. MARTINI MEANS FOR DRILLING 2 Sheets-Sheet 2 INVENTOR.

L60 A. Mar/'m' AGENT United States Patent MEANS FOR DRILLING Leo A. Martini, Dallas, Tex. Application February 6, 1957, Serial No. 638,652 Claims. (Cl. Z55-4.4)

This invention relates to a method of drilling and means therefor, and more particularly to -a method and means for alternately increasing and decreasing the relative downward pressure exerted by a drill string on a bit mounted on and rotated by the latter on the bottom of a subterranean bore.

The present application is `a continuation-impart of my prior application, now abandoned, filed November 7, 1955, and designated by Serial Number 545,25 6.

In the exploration for oil, the art of drilling well bore holes into subterranean areas of the earth has been widely investigated and extensively developed. The techniques employed are many, and a wide variety of drilling bits and associated apparatus have been developed. One conventional procedure is to attach a suitable bit on the end of a pipe string and to rotate the bit by the rotation of the pipe string. v

Thus, at the present time, the majority of drilling operations are conducted by employing rotary ldrilling equipment. In conventional rotary drilling, a hollow, jointed steel shaft `called the drill 4stem is rotated from the surface of the earth. This shaft, extending downwardly into the earth to any desired depth, rotates a drill bit. For a number of purposes, a weighted fluid called drilling :mud is circulated in one direction through the drill stem :and in the opposite direction .through the annulus between Ithe `drill stem and the bore hole.

In the past, cable drilling equipment also has seen wide use and has certain advantages, particularly where drilling in rock, but has generally been displaced by rotary drilling which is especially advantageous because it gives a high speed of penetration in relatively soft formations, and because it is suitable for use at great depths. Rotary drilling, however, is relatively inefficient in very hard formations, since rotary bits, even of the hard-faced or diamond-set types, are in such cases subject to a high rate of wear and require constant replacement. Cable tools, while most eifective in hard formations, are limited in their use to relatively shallow depths.

Previous proposals have contemplated giving -a reciprocating 4action to a rotary drill bit, and this has been done in several cases by mechanisms which raised and then dropped a b-it relative to the bore hole and to the drill string rotating the bit. While without doubt possessing merit, these mechanisms have tended to be costly and were to a certain extent subject to misalignment and to malfunctions caused by denting or bending of relatively long cylinders, piston rods, etc. with which they were provided. By necessity, they also tended to be expensive and complicated in construction and operation.

It is accordingly an object of the present invention to provide an improved method for alternately increasing and decreasing the relative downward pressure exerted by a drill string on a bit rigidly mounted on said drill string and rotated by the same at the bottom of a bore hole.

Another object is to provide an improved method whereby elastic, elongating deformation is repeatedly .elected in the drill string and each time followed by 2,905,439 Patented Sept. 22, 1959 ice elastic recovery of the drill string for increasing and decreasing its relative downward pressure on the bit.

A further object is to provide means whereby the impacting action of a cable tool is added to the grinding action of a rotary bit.

Yet another object is to provide means for elfecting repeated elongations, with-in its elastic limits, of a string of drill pipe on which is rigidly mounted a bit, each of said elongations being followed by elastic recovery of the drill string.

Still another object is to provide means such as stated above which are hydraulically operated by the drilling fluid customarily supplied to the bit.

An additional object is to provide means such as thus far stated in wh-ich the bit is mounted on the drill string rigidly and not through telescoping parts, thus assuring al-ignment of the bit and preserving its ability to drill a straight bore.

Still another object is to provide means of the above character which are simple and automatic in operation,

relatively easy and inexpensive to construct, and provided with lubricated and otherwise protected parts which as a consequence have a long working life.

Other objects and -advantages will become apparent from the specification and `claims and from the accompanying `drawings which illustrate an embodiment of the invention.

Briefly stated, the invention comprises a method for alternately increasing and decreasing the relative downward pressure of a hollow drill string on a drill bit rigidly mounted thereon while the bit is rotated by the drill string at the bottom of a bore hole, this being accomplished by elastic, elongating deformations of the drill string followed by elastic recoveries of the same which are produced by alternately restricting and allowing substantially unimpeded ilow of drilling uid Ithrough the drill string at a point considerably removed from its upper end. The invention further provides an eicient and desirable means for Iimplementing the use of the above method. The major elements of these means include: a continuous passage extending through a drill string and a bit mounted on the lower end thereof; highpressure means for supplying drilling fluid to the passage in the region of the upper end of the drill string; valve means in the passage at a `considerable distance from the upper end of the drill string; resilient means for biasing the valve means toward van open position thereof; and automatic means for varying the bias exerted by the resilient means on the valve means. The valve means is movable by drilling fluid ilowing through the continuous passage to a position wherein it substantially closes the passage. The automatic means may comprise an elongated tubular part rigidly mounted in the continuous passage, closed at its upper end, and having restricted communication at or near its lower end with the continuous passage. A piston slidably mounted in the tubular member is biased toward the lower end of the latter by means contained in the tubular member. This piston is operatively connected to the resilient means biasing the valve means and is movable, by pressure of fluid entering the tubular part, to a position wherein the valvebiasing means forces the valve means out of its position substantially closing `the passage and to a position wherein ow through the passage is substantially unrestricted. The piston is also movable, by the means biasing the same, to a position wherein the valve-biasing means allows closure of the valve means by the drilling fluid. Connection between the valve means and the resilient means biasing the same may be aiforded by a substantially non-stretchable member, such as a rod, slidably extending through the piston and the lower end of the tubular member into the interior Vof the latter above the piston. Wear on the valve means is minimized by provision'thereon of la resilient coating, and means is furnished for lubrication f the piston and the member connecting the-valve means to its .biasing resilient means. Ina [preferred embodiment of |theinvention,'.the .valve means' and automatic means'are enclosed in 1an outer cylinder through Hwhich the continuous passage' extends ndin'coinbination with which '-they-formatool which may berigidly mounted in a drill-string asaserial member thereof for instance, thetoolmmay constitute the lower member of a'drill string .and may have the bit rigidly mounted on'itslowerl-.end,` or Ialternatively may be mounted in Vthe drill string at some distance'above 'the bit. When the drilling uid closes the valyefmeans, hydraulic pressure lis'built up in the'fdrill stringY by the highpressure Vsource of drilling ilnid. This pressure effects elastic .elongation of( the drill .string above -the valve, -fthus increasing downward pressure fof the i drill string on the bit.` While the valve means remains'closed, drilling fluidmoves thepiston'toa position wherein the bias'on the Valve means'is so increased 'that it'is vforced open. When this occurs,.uid,pressure-inthe continuous passage is relieved asiluiditlerein 'resumes unrestricted ilow; `-the drill string achieves elastic recovery to Vits original length; and the piston is moved by itsl biasing means backV to Va position .wherein bias ,on the `valve means is small enough to la'gainallow .closurefof'the latter. i i f In the drawings, which illustrate. a preferred embodiment of the invention: A Y Y Figure l is a semi-diagrammatic View showing the drill string, high-pressure source. of drilling'fluiitool, and bit, the latter being in place in aV subterranean bore;

Figure 2 is a longitudinal sectional View of the tool, bit, and a fragment of theldrill string taken along line lll- II of Figure l; and I Figure is a cross-sectional view taken at the location designatedby line'lIl--lllof Figure 2 With reference nowto Figure 1, -a drilling facility includes a xture =rotatably supporting a drill string 1:1, the latter being madev to rotate by va power-driven table 12 of any conventional sort. The drillstring 11 extends downwardly into a subterranean bore 1 3,- and rigidly mounts the elongated vtool '14. On the lower end of the tool I4. may be mounted an additional section of drill pipe similar to 11; or, as `showin-the bit 15 may be securely fand rigidly mounted ldirectly on the lower end of the tool. The `drill stringvll, as will be further shown and described, is hollow and thus contains a passage utilized for supplying drillingtluid to the bit 1'5. This passage (lated more fully described) receives drilling fluid from a high-pressure pump 16 through a suitable conduit I17 which has juncture with the drill string 1'1 at a pointY preferably near the upper -end of the. latter. The pump 16 must be capable of delivering iluid to the drill string |11 at pressure such that, With vthe flow of fluid stopped at the tool 14, the hydraulic e pressure built up within thedrill string will be sufficient to effect enough elongating, elastic deformation of the same tosubstantially increase its relative ,downward pressure on the bit andfthus effect 'a corresponding increase in the,pressu re of the rotating bit 1'5 .on the bottom of the bore 13.

-With added referenceto Figure -2, the drill string 11 has a hollow interior 118 which extends from the -tool 14 to thepreviously described junctureof the drill string with the drilling-fluid supplying conduit 17.

The toolf14has an outer cylindrical part 19 preferably .provided with female threads v20. at its lower end for reception of matching threadsprovided on the upper end of thebit 15 and with,y male threadsf21 on its .upper end for engaging the female threads: customarily provided in the lowerrend of the drill string 11. The' internal diameter of the outer cylinder v19 mayvarysasbest suiting aparticular application, and conveniently may? be madei larger than that of the drill string. 1'1. At axmiuimllmit. and

parts therein should not unduly restrict the llow of drilling iluid which it will be apparent iiows therethrough from the drill string 11 to the bit i15, the interior of the outer cylinder 19 being open to and continuous with the interior 118 of the drill string =1.1. At its upper and lower ends, the outer cylinder 19 may be of an internal diameter approximately that o f the drill strings interior 18. An annular seat Z2 'is-provided near the lower end of the outer cylinder 19- above thethitfengaging lower threads 20. This seat 22 defines an opening therethrough which provides communication "between the'i-nte'rior of the outer cylinder 119 and an .axialpassage 23 fin the .b itleS. In the specific eramplefthe iiterir f the outer cylinder 19 has an upper-segment 124 whichextends downwardly to a point conveniently located somewhat below the upper threads 21. From this point, the cylinders internal bore llares downwardly and outwardly to the full diameter of its maior. oootfal,Porflon,-%,-Wbiob dlairlotor llolllobo Solllbilit for .Proporbboommolotlon otiolornalpafts. to be described. yFor' the lower endotfl V4his eritralportion 25, the lowerportion 21S-.of thebore mayfdiverge dewnf wardly and inwardly to. the seatvzg,

The seat 22 will best withstand the abrasive' etffeetspf drilling Hohl-.passing tborotllrollsllaotlftbo uoariiposod thereupon by tboxrolvofbolyl?. (tobo-dosoribtd) ifi! is made from orcoveredbyalayero( t material Such as onoiofbororioos. Sorts ofoatof, rubbers or o toogbg'olastoraorlo controlled. sob.-

ooo. of tho lluorooarbonolastomore. an. orafflol l which, biblia.- uorolbylooo. Probabili matliotosl- Toonf 'Tho convergent loworfsoeoioot 2,6 of'lbo. la? iorior of thooutor oylndor -1s91islmaol1i d torrovidoo o short counterbore 2.8 offaysizefer .snug eception ovfithe, seat 22 and on the lower end of whiehwthefseathnds support. y

For easeof, installation: ofjcornponents. installed therein, the outer oylindor 19. *11i-arbo modo" :oo Sootiolis.. 292 30, 31,- Tbus, tliooppbrfboromortloo @and tho lloro therebelowmay be contained ima-relatively short, upper? ond Section 2? -A oorrosporloiog.loworondfsootionrl may Contain the soot. llano tbolborob; dii/.oreille ,lower Portion 26.- yThosoobotforlo 12.9., Slohobld botllroaooslfas al 32 Vand 33foi' oogagemootwthfoort odios threads of a maior, obntmljportion 3,0. rbiolroo roo tho, Qontrol largerdianieter boro portion 2.5:,

A11 inner oylndrloloort is risidlrf,(andprotorably ooaxallyl mounted irlthoolltorloylinolor: for thi Por: pose it iS-provdod withoilotipborolly.dlopooosotfof lugs 36 loolool atorrloor its., oppor. ood. and .has a similarfsn V37 CFiguro. 3;) profe ably looatlodfat-ot nobr ils lower ond., Theologe-3.6., 3. oy bofatlxodito lille inner Cylinder; .3'.5 in any. Soollro and. .uitablo'fashion.- (fon example by woldtirigl ,l andA mustfbotlonseonoosh. tfbrioo fully the3 interval botwoo11-tllo-1wa1lsfof-lho two oylirlsof 19,65.. Thermes-.36, S'lraot opaoors-wbiohlrosltvoly prevent t lateral motion. otltbo, loner oylilldor. litl; tho outer cylinder-119,. 11nd,-.t11otoppor-logs.- More rmly lrotained against relativo ondwiso; motion of hof two Cyl.'- inders 35, 1.9i This 'lattorfproferably is,-aooomolioboo by counterborirlg tho ootoroyliilsor, 1.9, at its oppor .ono to. form anintornal shoulder 3.4 looafoslabolowtllotlouor end. olI the; threads. 52 of: the oppor-oodlsootior'?, .fTho upperloss 36 aro rigidly olompod .bota/ oon tbowshoulslor 34. and tho upporfond Sootion 29.2 Barberi. otr loroV 36; 37 .may comprise three ornato-memberseiner Elgar-o3 Shows tho bottom-sot to hai/oi four lugo Webtools/forested about tho periphery of 'tho -rlnoroy Hor 3,5-,

Astho inner cylindorhaszanovo dialnetorfwhiob is substantially Smollorlhon. tho -innor'diamotortfofttho coaxial.. outer oylindor 1.9, a s lobi'o'rlilso. Space 38; between the' juxaposed-walls yof QthQSeYcylinderS, fThis space v38v is continuousvwith theinterierofvthe outer cylinder 19.belovvand abovo @bionet-Cylinder 35 .aotlhus is continuous with. theblbioloriorziligoro 2).-and tho drillstring interior 1t?, all tbosooooorrlingly boina-parts of a single, continuous passage 39 which extends through the drill string 11, tool 14, and bit 1'5.

A piston 40 (Figure 2) slidably mounted in the inner cylinder 35 has a central, axial opening 41. Appropriate grooves are provided in the piston 40 around its periphery and within the opening 41 for receiving sealing rings 42A and 42B. The outer rings 42A seal between the pistion 40 and the wall of the inner cylinder 35; the inner rings `42B seal between the piston and a rod 43 to be described.

The inner cylinder 3'5 is closed at its lower end by a circular wall or plug 44 which is peripherally threaded for engagement of corresponding internal threads 58 formed in the lower end of the inner cylinder. The plug 44 has a central opening -45 which is coaxial with and of the same size as the central opening 41 of the piston 40. The material of the plug -44 defining central opening 45 is provided with one or more grooves coaxial with the opening 45 and utilized for receiving one or more sealing rings y50. Radially displaced from the plug opening 45 are one or more restricted passages or orifices 46 which communicate between the continuous passage 39 and the lower face of the piston 40. These orifices 46 may be in the form of passages drilled through the plug 44 and opening beneath the piston `40. Four such orifices 46 are shown in Figure 3.

A helical spring 47 (Figure 2) mounted coaxially with and in the inner cylinder 35 between the piston 40 and' a wall 48 which closes the upper end of the inner cylinder constantly urges the piston 40 toward the plug 44, which acts as a stop for limiting downward travel of the piston. This spring 47 is a component of a first, piston-biasing resilient means which further includes the air or other compressible iiuid trapped above the piston 40 and compressed by the same when it is moved upwardly.

The rod 43 has an enlarged upper end which may include a cross-piece 49 located interorly of the inner cylinder 35 and above the piston 40. The rod 43 extends downwardly through the piston and plug

central openings

41, 45 and should be of a diameter such that it is axially slideable in those openings, yet Well sealed by the Sealing rings 42B, 50. A passage 51 preferably provided in the rod `43 communicates between the interior of the central hole 45 of the plug 44 and the interior of the inner cylinder 35 above the piston 40. Threads 52 are formed on the lower end of the rod.

A tapped valve body 27, preferably of circular form, is rigidly attached on the lower, threaded end of the rod 43 is coaxial relation to the latter and the seat 22. The valve body 2'7 is of such diameter that when inserted into the seat 22 it snugly lls the same, thus interrupting thereat the continuous passage 39. In the example shown, the valve body 27 is made in the form of a sphere/of greater diameter than the seat 22, has a metallic core 54, and has an external skin or covering 55 made, as is the seat 22, of any durable, preferably resilient material such as previouSly mentioned.

The valve body 27 is biased upwardly away from the seat 22 by a second resilient means comprising a yhelical spring 56 footed on the piston 40, coaxial with the rod 43 and the piston spring 47, and engaged at its upper end by the rods vcross-piece-49. The valve spring 56 is of smaller diameter than the piston spring 47. Connection between the valve body 27 and its spring 56 is` effected by the rod 43. This spring 56 may be made of a material which is rectangular in cross-section in order that it may better endure axial loads, imposed after its full compression, without buckling.

-It thus may be`seen that the spring 5,6 is a resilient means which urges the valve body 27 away from the valve seat 22, and as the spring 56 is footed on the piston 40, upward movement of the piston 40 willtend to compress the spring 56 and consequently increase its upward force on the valve body 27 through the rod 43. Y

At this point, it may be noted that the plug 44 is preferably of such thickness that the lower end of the oil passage 51 will not leave the plugs central hole 45 when the valve body 27 is moved to its upmost position. This is desirable for the prevention of the delivery of oil to the inner cylinder 35 below the piston 40 via the passage 51 The bit 15 may be of any sort well suited for rotary drilling and provided with a passage 23 communicating as described with the interior of the outer cylinder 19 and opening, near its bottom, into the wellbore 13 (Figure l).

From the above, it will be seen that, in the example shown, the valve means includes the valve body 27 (Figure 2) `and seat 22. The resilient means for biasing the valve means toward its open position is the smaller-diameter spring 56. The rod 43 provides a means for con- -necting this resilient means to the valve body 27. The

automatic means for varying the bias exerted by this,

resilient means on the valve means includes the inner cylinder 35, piston 40, and the spring 4'7'and volume of compressible fluid above the piston 40. `It will be understood that the valve means may be located at any point in the drill string 11 (Figure 1) which is far enough removed from the upper end of the latter to secure sulicient elongation of the drill string during operation (to be described) of the device. Thus, the valve means, automatic means, and valve-biasing resilient means may be located in a drill bit made to receive them. Alternatively, the valve means may be located in the bit 15 (Figure 2) and the automatic means and valve-biasing resilient means in the drill string 11 immediately above the bit, connection between the valve means and its biasing resilient means being maintained by the rod `43.

On the other hand, as in the example shown, the valve means, its resilient biasing means, and the automatic means may be located at the lower end or within the length of the drill string 11. To pro-vide a sturdy, troubleree mechanism, it is generally desirable to make the inner cylinder 35, valve seat 22 and body 27, etc. of generous size, and this is made possible by locally enlarging the diameter of the continuous passage 39. To this end, the outer cylinder 19 may be made larger in diameter than the balance of the drill string 11, and the resulting structure comprises a tool 14 which may be rigidly installed in the drill string 11 to form a serial member thereof.

The operating life of the device will be prolonged by lubricating sliding of the rod 43 through the piston 40 and plug 44 and of the piston 40 through the inner cylinder 35. To this end, a layer of lubricating fluid 57, such as a suitable mineral oil, is provided in the inner cylinder 35 above the piston 40. Oil on the cylinder wall lubricates movement of the piston 40 thereagainst, and oil on the rod 43 similarly facilitates sliding of the latter through the piston 40. The oil passage 51 in the rod 43 is preferably made long enough so that, with the piston 4) near the plug 44 and the valve body 27 seated, its upper end is above the level of the oil 57, while its lower end remains within the plugs central opening 45. The upward extension of the oil passage 51 must be limited to a dirnension such that its upper end will be submerged in the oil 57 before the piston 40 has entirely reached the top of its stroke.

plugs central opening 45. Although such is not shown, this lubrication of the plug 44 and rod 43 may be improved, when found needful, by the inclusion of a wick, such as is well known, in the oil passage 51.

In operation, the bit is rotated in well-known fashion on the bottom of the bore 13 (Figure l) by the table 12 and drill string 11. The pump 16 delivers a flow of drilling uid through the conduit 17 and continuous passage 39. (Figure 2) to the bottom of the bit 15 for improving operation ofthe latter.

As the stream of drilling fluid flows through the continuous passage 39 past the valve body 27, it exerts forces upon the latter which move it downwardly against resist-` The passage 51 thus receives oil 57 which is de-V livered through its lower end to the wall defining the anceof the valve-biasing spring 56. As thevalvebody 27 nears the seat 22, the restriction it imposes uponlthe flow of 'fluid rapidly increases. The pumpcontinues to supply fluid to the drill string at -a -rate which, but for the resttiction of the flow by Ithe valve body 27, would be unchanged. As a consequence, fluid pressure in the continuous passage 39 above the valve body 27 increases, while it tends to decrease below theibody 27. 'The sharply increasing vpressure increment across the valve lbody'' causes the linalvportion of its-downwardstroke-to be quite rapid, and it therefore seats with asna-p, whereuponv the downward momentum ofthe drilling'fluid and therapid increase of hydraulic pressure which -is effected by the continuously running pump exert-strong forces internally of -the continuous passage 39 above the -valve seat 22 rwhich effect an elastic elongation or stretching of the wholedrill string 1-1 above the valve seat. Thus, some'of the inertia of the drilling uid and weightfof'the drillstring 1.1, sustained by the-supporting meansflll (Figure l.) before the stretching, is transferred with asharp -impact to the bit 15 (Figure 2). Since thearnount of lengthwise stretch for a given linear foot lof the drill string Y11 will be -quite small, it is obvious that thelvalve means mus-tbe located a considerable distance lbelow-the top offthe continuous passage 39 in order that the total-tendencytoward elongation experienced along the Vdrill string 111 -will Ybe large enoughto yield the desired increase of-d'ownward pressure on the bit 15.

As soon as-pressure in the continuous passage -39 rises high enough to overcome resistance olered bythe -piston-biasing spring 47, lluid begins to ilow-into-the -inner cylinder 35 from the passage 39 'through theivorilices 46 in the lower-end wall 44. This flow raises the piston 40 against pressure of the piston-biasing spring 47--and air orother compressible fluid in -the inner cylinder 3-5 above the piston. In moving upward, the piston .-40 also must -further compress the valve-biasing spring 56, and in so doing it increases the force vwith which the valve lbody 27 is urged away from the seat 2-2. The lower-face area of the piston 40 must "be large enough, relative to the valve body 27, to ensure that downward forces on the vvalve body will be overcome bysupward forces exerted on the latter by thepiston through the rod 43 and valve-biasing spring 56. The :rapidity Iwith which 'this occurs is regulated -by the vcolleetiv'ejsize of; the orifices 46. Thus, if the orilices Adare smaller, the allow-of duid throughthemfinto the inner cylinder will be slower, and a longer 'time interval willbeconsumed inraising the piston 40 to a point at which -downward forces Yon the valve body 27 are-overbalanced.

`When the point just deiined-is reached,-the-valve body 27 will move upwardly above the-

seat

2,2. 3If this motion resulted in no pressure changes in the continuous passage 39, the valve body 27 would move upwardly only until Athe unchanged, downward forces exerted thereon could come into equilibrium with-thevalve-biasing spring 56. As soon as'the valve body 27 moves alittle wayout of the seat 22, however, uid ows yinto the -bit V15, thus relieving some of the pressure in the Apassage 39 above the valve body. The pressure increment across the valve body 27 is thus reduced, thus increasing-the net upward force Jon the valve body. As the valve body 27 moves further upward, this process'progressively continues 1until the valve body is ywell away from -the seat. Consequently, the spring 56 actually Vis able to move -the valve body 27 quickly and vigorously l.to its open, 4fully raised position wherein it is well removed from thevalve seat 2-2. The full Vflow of -lluid into vthe bit 1'5 throughthe seat 22 thus is quickly resumed, fluid pressure above the seat drops substantially to that in electfbefore clo sure of the valve means, and the elastic properties'o'ffthe material (steel, etc.) of which the drillstring vr11 'is 'made eifect 'its It'ull recovery to its original length.

'Return of the piston 40 -to its position wherein-minimum force is exerted by the smaller-'diameter spring 56 on the valve lbody 2.7 is `etlected by the fluid and larger spring 47 compressed inthe inner cylinder 35 above the piston `4|) and also, in some degree, by `downward pressure of the smaller :spring 56. The rate at which the piston 40. 'is forceddwnward is limited by the rate of flowrofdrillingluidlout 'of the inner cylinder 35 through the oriiices vd6, and 'ihence is controlled by the collective size .of sthe rlattei'.

When the lpiston 40 has travelled far enough downwardly for downward forces exerted on the valve body 27 by the flow of drilling fluid through the continuous passage 39].to override v'the -upward force -exerted by the valve-'biasing spring 56, the valve -body 27`will be moved downwardly'and .resseated in vthe seat 22. Thus, the whole .cycle will Ioccur `over and rover again, and the Arepeated impacts V-andperiods of downward pressure o n the .bit 15, combined .withlthe periods in which elastic recovery of .theJdrill :string 111 occurs, vgive the bit a reciprocating actionkwhicln added to its Irotary action, much improved-ts oper-ation, especially in hard formations. I

'When the pump .is-shutoff to halt the flow -of drilling lluidrto the .drill string, fluid v.may not llow past vthe valve body 27 with enough impetus to force it `into the seat 22. In such a case, lall .drilling .liuid -will fbe automatically drained through the bit 15 until -no more remains in the .continuous passage '39 or until it is level with drilling uid Vin the well lbore. Where -the column Vof fluid is sufficiently .'high, when `the pump is -shut oli, to cause seatingtof .the valve body 27, `the -device' will go through :its cycleiof operation u ntil the' uid column `is reduced toa height at which Anot enough flow occurs to seat the'valve body 257. 'The remainder -of -vthe lfluid then will drain into -thewell bore through theibit 1-5 without interruption. 'Thesi'ze of the piston 40 is such that .the upward fforce it. can exert, when -ful l pressure of .the drillingud is .directed to it, 'is flarge enough lto achieve unseatingsof the valve body 27 at and beyond all times that vthe .column of' uid is capable of reseating it, Thus', the valveibody-Z'f :always stops-operation while unseated, and full drainage offthedrilling lluid through the bit 1'5.-when the .pump is .shut off is automatically accomplished. 4

While the foregoing fully describesapreferred embodiment of itheinvention, it vwill `=be `evidentAtha'tlrernoval of the large piston-biasing spring .-47 `willlnot render the device inoperative, so long as the vsmaller spring 56 is of proper springarate andleugth, but instead -will result in astill more vsimple andeconomically constructed form of the invention'. In operation of this form of the-invention, the initial seating .of the `valve 'body 27 in the seat 22 occurs as previously deseribed,-and Athe piston 40l is .in the same waydrivenupwardlyby `lluid rforced -thereagajnst `through theorices 46,. The upward movement of the vpistonfm) is, however, resistedfonly by the smaller spring 56 andby. the air :entrapped above Vthe -piston 40 in the inner cylinder 35. Thus, the spring A56 isa resilient means for biasing .the `valveibody '27- to its open position and Aalso for :moving ithe -piston 140 toward lits lowermost .position wherein minimum bias Yis imposed upon the valve body. 2 7. Whenfthe piston 40 .has moved upwardly to .a Apoint at which expansive forces in .the spring 56 overcome' downward --forcesV imposedy by the drilling iluid lon the vvalve body 27., or -when vthe spring 56 becomes Yfully'compressed, the valve body 27 -is moved upwardly as .-previouslydescribed and .is stopped inits upward Atravel -by contact with the bottom of the -plug 44. The piston 40 then is moveddownwardly `by the energystored in the spring-56 and in the'air compressed above the piston. 40. When-the lower end of the spring 56, footed onv'the piston 40, hasmoved downwardly far enough, a Ypoint is reached -at which downward -forces exerted on the vvalve body 2 7 'by' Athe yllow ofV drilling fluid override upward forces exerted onthe valve -body 27 by the spring l56, and at this point the valve body 27 is seated as before against resistance of the spring 56. This cycle of operation continues as long as the flow of drilling iluid is supplied to the continuous passage 39.

While a novel and efcient mechanism has been disclosed together with a modification thereof for carrying out the method of the invention, it will be clear that the method is not restricted to application only where a mechanism such as described is used for carrying it out. Instead, the method will be found advantageous whenever other ecient means which might be made available (for instance, an electrically timed and operated footvalve) are used, through it is doubtful that such other means could offer the advantages of the simple and efficacious means herein provided. Other forms and modications of the present invention, both with respect to its overall arrangement and the details of its respective parts, which wi'll become apparent to those skilled in the art after reading the foregoing description taken together with the drawing, are intended to come within the scope of the invention as more particularly set forth in the appended claims.

I claim: 1. For intermittently increasing the downward pressure of a drill bit on the bottom of a subterranean bore, said bit being rigidly mounted on the lower end of and rotated by a drill string supplied with drilling fluid under pressure, a device comprising: a passage extending through said bit and drill string and used for receiving and conducting said drilling fluid; a valve seat in said passage in the vicinity of the lower end thereof for the ow of said drilling fluid therethrough; a valve element upstream of said seat in said iluid and movable by ilow of the latter to a closed position wherein said valve means substantially closes said passage for allowing an increase of hydraulic pressure in the latter which eiects elastic elongation of said drill string and thereby increases the pressure of said bit on the bottom of said bore; a cylinder rigidly mounted in said passage, said cylinder having a first, closed end and further having a second end through which communication is provided between the interior of said cylinder and said passage; a piston slideably mounted in said cylinder; and resilient means interposed between said piston and said valve means, said resilient means being operative for imposing a bias on said valve means toward an open position thereof wherein said passage is substantially'unobstructed by the latter, and for biasing said piston toward a position thereof wherein said bias on said valve means is reduced to a value permitting moving of said valve means to said closed position thereof by said drilling Huid, said piston being movable by said drilling fluid to another position thereof wherein said b-ias forces said valve means to quit said closed position thereof.

2. Forl intermittentlyV increasing the downward pressure of a drill bit on the bottom of a subterranean bore, said bit being rigidly mounted on the lower end of and rotated by a drill string supplied with drilling uid under pressure, a device comprising: a passage extending through said bit and drill string and used for receiving and conducting said drilling fluid; a valve seat in said passage in the vicinity of the lower end thereof for the ow of said drilling uid therethrough; a valve element upstream of said seat in said fluid and movable by ow of the latter to a closed position wherein said valve means substantially closes said passage for allowing an increase of hydraulic pressure in the latter which eifects elastic elongation of said drill string and thereby increases the pressure of said bit on the bottom of said bore; resilient means for exerting a bias upon said valve means toward an open position -thereof wherein said passage is substantially unobstructed thereby; a cylinder rigidly mounted in said passage, said cylinder having `a rst, closed end and further having a second end through which communication is provided between the interior of said cylinder and said passage; a piston slideably mounted in said cylinder and operatively connected to saidresilient means for varying said bias exerted by the latter on said valve means, said piston being movable by pressure of said drilling fluid to a position wherein said bias forces said valve means to quit said closed position thereof, said piston being movable to a second position wherein said bias is reduced to a value permitting moving of said valve means to said closed position thereof by said drilling iluid; and other resilient means biasing said piston toward said second position thereof.

3. A device of the character claimed in claim 2, said communication between the interior of said cylinder and said passage being through at least one opening provided inrsaid cylinder below said piston and of a size restricting the rate of a flow of drilling iluid into said cylinder which occurs when said valve means is closed.

4. A device such as claimed in claim 3, said other resilient means including -a compressible fluid enclosed above said piston in said cylinder.

5. A device `such as claimed in claim 3, said other resilient means including Ia helical spring compressed between said piston and said rst, closed end of said cylinder.

6. For intermittently increasing the downward pressure of a bit on the bottom of a subterranean bore, said bit being rigidly mounted on and rotated by the lower end of a two-ended drill string, an apparatus comprising: a continuous passage in said bit and drill string, said passage communicating with said bore in the region of the lower end of said bit; means for supplying drilling uid under high pressures to said passage in the region of the upper end of said drill string; a valve seat near said lower end of said passage and passed through by the latter; a valve member movable relative to said seat by ow of said uid through said passage to a position wherein it substantially closes said passage and restriction of said llow by said valve member occasions an increase in hydraulic pressure in said passage accompanied by elastic elongation of said drill string and increased downward `pressure of said bit on the bottom of said bore; resilient means for exerting a bias upon said valve member toward an open position thereof wherein said ow of fluid through said passage is substantially unrestricted by said valve means; and a movable member contacting said resilient means and said drilling fluid, said member being responsive to the pressure thereagainst of said fluid for moving said resilient means in accordance therewith, said member being ,distinct from said valve member.

7. A well tool adapted for serving as the lowermost member of a l.drill string rigidly mounting and rotating a bit at the bottom of a subterranean bore, said tool comprising: yinnerand outer tubular parts spatially xed relative to each other;` means for connecting upper and lower ends of said outer part to the lower end o-f a hollow drill string and to the upper end of a bit having a passage opening into said subterranean bore; a chamber formed between said inner part and said outer part, said chamber having free communication with the interior of said hollow drill string; a seat in said outer tubular part providing communication between said chamber and said passage in said bit; a piston slideably mounted in said inner tubular part; means closing said inner tubular part at an end thereof lying on one side of said piston; an orifice providing restricted communication between said chamber and the interior of said inner tubular part on the other side of said piston; resilient means resisting movement of said piston away from said orice; a valve body seatable in said seat for interrupting communication between said chamber and said bit; and resilient means connected between said piston and valve body and operative for urging said valve body away from said seat.

8. A well tool such as claimed in claim 7, contacting surfaces of said seat and said -valve body being covered by a durable, resilient material.

9. In ,a .well drilling facility including a-drill-string having upper and lower-ends, `afhigh-pressure source of drlilling fluid, and -a bit rigidly mounted on the lower-end ofsa'id drill string and rotated -thereby -at vthe bottom -of a subterranean bore, 'a device comprising: `a continuous passage in said drill string and bit, said passage 'having communication with-said subterranean bore in-the region of the lower end of said bit and connected inthe neighborhood of said -upper end of said drill string to said source of high-pressure fluid; an annular- -seatin said passage -and providing-communication between -upper and lower portions thereof., said seat being remote -from-said upper-end of-said drill-string; an elongated tubular `member rigidly mounted in said passage above said seat and having an outside diameter substantially smaller than the diameter thereat of said passage, said tubular member having a closed upper end-and a wall across its lower end; at least one orice providing communication between said -passage-and the interior of said tubular member through said-wall; a piston slideablein said tubular member; means for sealing between said piston and said tubular member; first resilient means resisting movement of said piston Itoward said closed upper end of said tubular member; a rst opening extending from said passage into said tubular member through said wall across said lower end of the latter; a second opening coaxial with said first opening and piercing said piston; a rod having upper and lower ends and extending slideably through said first and second openings, said upper end of said rod being adapted for engaging a helical spring; means for sealing between said rod and said Wall and between said rod and said piston; second resilient means comprising a helical spring compressed between said piston and said upper end of saidrod; and a spherical valve body rigidly mounted on said lower end ofV saidy rod, said -valve body being movable downwardly againstY resistance of -said second helical spring -into said-"seat for substantially interrupting communication between said upper and lower portions of said passage.

10. A device such as claimed 'in claim 9,' said -rst resilient means comprising a compressible uid contained in said tubular body -above said piston.

ll. A device such -as claimed -in claim `9, said first resilient -means comprising a helical spring compressed between said vpiston and said closed upper end of :said tubular body.

l2. A device such as claimed in claim 9, said first resilient means comprising a helical spring compressed between said piston and said closed upper end of said tubular body-and further comprising a compressibleuid contained in said tubular 'body above -aguantity of lubricating liquid lying on said piston.

13. In combination with a hollow drill string having upper and -lower ends., a high-pressure source of drilling liuid, and a Ibit rigidly mounted on the lower vend of'said drill string and rotatedthereby at the bottom rof Ia subterranean lbore, said bit having a passage ifor the reception of -drilling luid and for the discharge -of the same into said zbore, a device comprising: an outer cylinder provided with means -for rigid connection thereof at its upper end to said drill string and at its lower end to said big-the interior of said outer cylinder having communication with the hollow linterior of said drill string; an annular seat inl said outer cylinder near the lower end thereof, said seat deiining an opening affording -communication between said interior of said outer cylinder and sa'id passage -in said bit; an inner cylinder having upper and lower end walls and rigidly fmounted in saidl outer -cylinder in spaced, coaxial relation thereto; a Vpiston -slideably mounted in said Vinner cylinder; means forl sealing between said piston and said `,inner cylinder; coaxial openings centrally piercing said lower end wall' and said piston', a rod extending through Vand slideable` in said coaxial openings; means for sealing between -said rod .and said `piston .and lower end wall; a plurality of --restricted openings communicating between 'the `lower face of said piston -and the exterior of said inner cylinder; resilient means urging said piston toward said -lower end'wall, said resilient means including a compress'ible fluid contained in said inner cylinder above said piston and a helical spring compressed between said upper end wall and said piston; a helical spring footed on said piston and urging said rod upwardly; -a spherical body rigidly mounted on the lower end of said-rod and movable against resistance of said helical spring into said vseat for interrupting communication between said outer cylinder and'said passage in said bit.

14. -A device such as claimed -inclaim 13, said device further comprising a lubricating liquid contained in said inner-cylinder above said piston, said rod having a passage through which said lubricating `liquid is supplied to -said '-lower end wall where 'the latter is in sliding contact with said rod.

r:15. A devicesuch as claimed in claim 13, said seat being lined and said spherical body being covered with aresilientv material.

References `Cited in the le of Athis patent UNITED STATES PATENTS 842,049 Wolsk Jan. 22, 1907 2,388,741 Hays NOV. 13, 1945 2,422,031 Mertin June 10, 1947 2,713,472 Bodine July 19, 1955 2,746,721 Moore May 22, 1956 2,780,438 Bielstein Feb. 5, 1957