US2620162A - Hammer type rotary rock-drilling bit - Google Patents

Description

Dec. 2, 1952 H. PENNINGTON HAMMER TYPE ROTARY ROCK-DRILLING BIT 3 Sheets-Sheet 1 Filed Nov. 16', 1946 INVENTOR. HAR Y PENN/N6 V m fl-rroRNEy Dec. 2, 1952 H. PENNINGTON 2,620,162

HAMMER TYPE ROTARY ROCK-DRILLING BIT Filed NOV. 16, 1946 3 Sheets-Sheet 2 INVENTOR. lhK/ey Paw/1 To Patented Dec. 2, 1952 UNITED STATES PATENT OFFICE HAMMER TYPE ROTARY ROCK-DRILLING BIT 8 Claims.

This invention relates to a hammer type rotary rock drilling bit for the drilling of bore holes for oil and gas wells, for example, which has proved to be successful in use and has resulted in reduced cost of drilling and the drilling of deep bore holes through rock formation without twist-ofis or fishing jobs.

The invention is an improvement of the hammer rock bit forming the subject matter of my Patent No. 1,892,517, patented December 27, 1932.

It is an object of my invention to improve the construction and operation of the hammer of said patent.

It is one of the objects of my invention to provide an auxiliary circulation of flushing fluid in addition to that employed in reciprocating the hammer by imposing a fluid pressure on the interior of the hammer case to cause a discharge of said fluid through auxiliary discharge ports in addition to the flushing fluid employed to operate the hammer and discharge through the nozzles of the cutter.

Another object of my invention is to provide means for selectively regulating the volume of such .by-passed fluid discharge for the augmentation of the volume of the fluid circulating through the hammer and the nozzle of the cutter to provide the fluid desirable for elevation of the cuttings in the annular space outside the hammer case.

It is another object of my invention to improve the construction of the valve mechanism of the hammer.

It is a further object of my invention to cause the closing of the port through the chuckv by means of the valve and to cause the motion of said valve to close said port to be caused by imparting a downward movement to said valve by means of said hammerand to seat said valve to shut off the flow of fluid through the nozzles by the inertia of said valve resulting from the downward motion of said valve caused by said motion of said hammer.

It is a further object of my invention to provide means in said hammer to control the length of stroke of said hammer.

It is a further object of my invention to control the stroke of said hammer by providing for the unseating of said valve from its seat upon a predetermined length of stroke of said hammer, and to provide for the retraction of said valve by means of a spring with means for regulating the tension of the spring for the purpose of regulating accurately the length of stroke and the speed of striking of said hammer.

It is a further object of my invention to pro- 2 vide for sufiicient flexibility in the valve stem to permit said valve to seat properly upon the chuck to shut ofi the passage of fluid through thecutter nozzles irrespective of variation in the axial alignment of said hammer and said chuck.

It is a further object of my invention to provide for a resilient .seat for said valve upon said chuck to limit the shock of the striking of said valve against said chuck and said hammer upon the reciprocation .of the hammer.

These and other objects of my invention will be understood from the further description of this invention by reference to the drawings, in which Figs. 1a.. 1b, and 1c are vertical sections taken through consecutive longitudinal. portions of said hammer chuck and bit;

Fig. 2 is a top view of Fig. la;

Fig. 3 is a section taken along line 3-3 of Fig. 10.;

Fig. 4 is a section taken along .line 4-4 of Fig. 1a;

Fig.5 is a section taken along the line 5'5 of Fig. 10.;

Fig. 6 is a section taken along the line 6-45 of Fig. 1a;

Fig. 7 is a section taken along the .line l-'I of Fig. 1b;

Fig. 8 is a section taken along the line 8-8 of Fig. 10;

Fig. 9 is a bottom view of Fig. 1c with cutters removed;

Fig. 10 is a section taken on the line Ill-la of Fig. 1b;

Fig. 11 is a fragmentary sectional view similar to Fig. lb, but showing the hammer elevated and the valve seated on the chuck;

Fig. 12 is a view similar to Fig. 11 but with the valve retracted;

Fig. 13 is a view similar to Fig. 11 with the hammer seated and valve unseated;

Fig. 14 is fragmentary in part section of a modified valve construction;

Fig. 15 is a fragmentary illustrative view of the valve on its seat; and

Fig. 16 is an illustrative view showing the hammer just starting upward.

In Figs. 1a., 1b and 1c, numeral I designates the hammer case which at itshead 4 is vformed into abox tool joint 2 adapted to be attached to the lower end of a string of rotary drill tubing through which flushing fluid is pumped downwardly. The case head is provided with aconcentric bore 3 the lower end l6 of which is enlarged and serves as a hammer cylinder. The bore is closed at its top except for theports 6 which connect the interior thereof with the annular space between the case and the bore of the well. The case has a central tubular section forming acentral chamber 8 and in this chamber thehammer 9 reciprocates. The hammer at its top is reduced in diameter forming a head II) which operates as a piston in hammer cylinder IS. A slight clearance I is provided between hammer head and the wall of the cylinder. The hammer head is provided with a vertical fluid passageway I4 for flushing fluid which through ports I2 is connected with thecentral chamber 8 of the case and serves as a bypass to pass flushing fluid from said chambe upwardly through the head of the hammer, through thebore 3 and then throughports 5 into the annular space between the case and the bore of the well. Owing to the fact, that theports 5 connect with the well bore in which the pressure of flushing fluid is always lower than that in thecentral chamber 8, the pressure in thebore 3 is also lower than that inchamber 8. This differential pressure is what causes the hammer to be raised during its reciprocation, as will be explained below. The lower end II of the fluid passageway I4 is separated from the main body of the passageway by means of a replaceable bushing or choke I3 which serves as a convenient means to control the amount of flushing fluid flowing through the passageway. A compression spring I1 is mounted in thelower end 16 ofbore 3 and abuts against the choke I3. This spring tends to move the hammer downwardly.

In order to supply flushing fluid to thecentral chamber 8 of thecase ports 6 are provided in the case head which pass downwardly around thebore 3 as shown in Figs. la, 2 and 3 of the drawing, the fluid then passing between splines I which separate the hammer cylinder from the case wall, see Fig. 4.

Thehammer 9 is slidably mounted in case I with sufficient clearance throughout its length to provide for circulation of fluid in the annular space between thehammer 9 and case I. It is guided at its lower end by means of wings or splines 42 on the exterior wall of thehammer 9 below the tapered portion of the hammer at the lower end thereof. The splines are of such diameter as to contact the walls of the case I and to provide circulation of fluid between the said splines. The hammer is provided at its lower end with a central bore I9 which connects with a central bore of larger diameter both of which are axially disposed in thehammer 9.

At the upper end of the bore I9 is provided a plurality of cross bores 2 I, shown as four in number, through whichpin 23 may be passed selectively as desired. Thuspin 23 may be introduced into any of thebores 2|. Thepin 23 passes through aneye 22 connected to aspring 24 which is in turn connected at its lower end to the top of thevalve stem 25 slidably mounted in thebore 20. Thepin 23 and bores 2I serve as an adjustable fastening means for the upper end of the spring. The bore I9 thus forms a spring recess or chamber and thebore 20 forms a valve stem recess or chamber. A reciprocatingvalve 26 is mounted at the bottom ofbore 20. Thevalve stem 25 is composed of ayoke 21 formed with aslot 28, as shown, carryingexternal grooves 28a formed throughout the length of the yoke. Theyoke 21 is connected to acylindrical section 33 of reduced diameter which in turn is connected to thevalve 26.

As will be observed the yoke is tapered with its widest point at 3| in slidable contact with the walls of thevalve recess 20 and the narrowest portion of thetaper 32 at the top of the yoke. Owing to the tapered construction of the valve stem the valve has a limited oscillatory motion about the point CH of maximum diameter serving as a pivot. The end of the valve stem is formed with ashoulder 34 and a section of reduced diameter 35 and carries tworesilient rings 37, such as rubber rings, between which theshoulder 38 of thevalve 25 is held and locked in position bylock ring 39. The face of the valve body is tapered beginning at its lower face. Midway the angularity of the taper increases at 26, and then increases again at 26 to form the seating section of the valve body.

An alternative construction is shown in Fig. 14 wherein the rubber rings, shown in Fig. lb, are replaced bysprings 39a. The washer 39b slidably abuts theshoulder 34 and is pressed against the shoulder by thespring 39a which rests on theinternal shoulder 38. Thesecond washer 390 seats on thelock ring 39 and abuts thelower spring 39a.

In both forms thevalve body 26 is free to float on the resilient mountings whether they be the rubber rings or the metallic springs. In the case of the metallic springs, the washers, seating against theupper shoulder 34 and making a close but sliding fit with thevalve body 26, prevent any leak past the valve.

Cross bores 29, shown as three in number, are formed in the wall of the hammer with centers upon the center line of thebore 20. Apin 30 may be passed through any of thebores 29 to pass across theslot 28. Thispin 39 and bores 29 serve as an adjustable means for limiting the downward motion of the valve and its stem relative to the hammer.

The lower end of thehammer 9 carries an enlarged bore which has an internal tapered surface 4Ia to form a valve seat for thevalve 26. The taper of surface 4Ia is parallel to the upper taperedsurface 26 of thevalve body portion 26. Thus, anannular chamber 34 is formed between the tapered surface Ma and the lower tapered surface of the valve body. The port II is provided in the lower end of thehammer 9 above thevalve 26, connecting the chambers I9 and 20 with the annular space between the case I and thehammer 9.

Thehammer 9 seats upon achuck 48 positioned within the case I the top of which serves as an anvil. Thechuck 48 carries a central bore orport 58 of smaller diameter than the valve chamber to form aseat 49 for thevalve 26 on top of thechuck 48. The inner diameter of case I is less, contiguous to the chuck, than the internal diameter of the case I at the hammer, thus forming aseat 43 the purpose of which will be described below.

The case I is screwed by a box and pin tooljoint connection 44 to the drivingsection 45. The end of the pin forms aseat 41 forrings 50 for purposes later described. The driving section carries splines 52 which engage withsplines 53 formed upon the exterior wall of theenlarged portion 5| of thechuck 48. These splines serve as means providing relative longitudinal movement between the case and the chuck to rotate the chuck and hence the bit orcutter head 51. The chuck carries rings 50 positioned in suitable recesses and making a sliding contact with the wall of case I. The ends of the drivingsection 45 abut against theshoulder 54 formed on the enlarge-d portion of thechuck 48; The.cutter head 51 is connected to the chuck by means of a box and-pin screwconnection 56. This cutter head carries thenozzles 59 and.cutters 6| removably mounted inT slots 60 and secured bybolts 62 positioned on each of the separatelyremovable cutters 61. The cutter head does not form a portion of this invention and is further described andclaimed in my co-pending application Serial No. 710,357, filed November 16', 1946.

The operation of the hammer bit is as follows:

The cutter is-rotated by the drill tubing from the. surface, employing the turntable conventional in oil well drilling, and drives the cutter through the splines. 52 and 53. It will be observed that during the rotation of the drill chuck through thesplines and during: the reciprocation oithe: hammer, the weight: of the string of drill tubing, or: so much thereof as the driller desires to impose on. the drill, is imposed on. the drill, since the. drill string and. case rest on the shoulder 54'. Mud or other drilling fluidv is: continuously pumped down the drill. pipe, as is conventional in. drilling practice. The. circulation of drilling fluid. is down the drill pipe. through. 2., via. conduits 6., and annular space; between the.hammer 9 and the case wall.

Since. the porter bore 58 is: in. communication with the: annulus between the. drill and bore. hele wallthrough. thenozzles 59* and chamber- 3: is; in communication with the said: annulus: through theports 5,. the static pressure at: thenozzles 59 andchamber 3'. is substantially the static pressure. of the fluid in the bore hole.

The drill piperis connected to thehammer case i. a112, and the. pressure in the drill pipe gen eratedthe mud pump. is communicated to the interior of the case. i via ports-'65.. With the valve off the seat: 49, the. static. pressure inside: the case andthe. bore of. the chuck, is thus. also that existing'in the. annulus. With the hammer (see: Fig. lb) seated on thechuck 48. and the valve seated on the.seat 49, the fluid: pressure inside the case I exerted by the mud pump down the. drill pipe is transmitted via. port. 4| inside. the bores I19 and 20. Venting of this. pressure vianozzles 59. is prevented by the sealing rings 50. Thepressure is. also exerted via port t2 via; the:- choke I3 and the restricted channel I5 t6" which, however, is in turn vented to the annulus via ports 5'. Thus the. static pressure-of: the annulus. is exerted on top of. the hammer and the higher pump: pressure within the drill pipe. and. bit is exerted inside. the hammer in bores I9 and The fluid pressure. exerted down the drill.

pipe into case I' thus elevates. the hammer, the

pressure in the case I, withvalve 26 seatedonseat 49 during the lifting of the hammer, being. higher than the static pressure in the; annulus; while the pressure in thechamber 3 remains at: substantially the static pressure in the annulus: dueto the ports. 5.

The pressure of the fluid inside the. drill pipe and exerted above the valve in therecess 20 is. greater than the-pressure in the bore hole. and; in the bore 58'underneath the valve. The seated" valveand therings 50 close communication between the drill pipe and port I5 and thebore 58". The pump pressure is thus exerted on. top of thevalve 26. The pump s pressure rising' causes-air elevation of the hammer as the pressure increases inside the recesses I9 and 20, and the valve remains seated on itsseat 49 on the chuck while the hammer is" elevated. The. hammer'thus' rises over. the valve stem, lifting thepin 30 until it engages the upper: end of the slot. 28 (see Fig. 11)

During all this time pressure in the case I is maintained by fluid flow down the drill pipe. When the pin engages the top of the slot the continued upward motion of the hammer lifts the valve stem and the valve is lifted from its seat onthe chuck. The valve having been unseated communication is established between theport 58 and the fluid circulating down the case I discharges throughport 58 andnozzles 59. Pressure thus falls in the annulus between the hammer and the case I. The pressure in therecesses 20 and I9 is vented through 4I into the annulus. There being a pressure equalization between the fluid inside the case and under the hammer and in chambers l9 and 20, the valve is retracted by thespring 24 against its seat 4Ia (see Fig. 12). The hammer drops under the influence of'gravity and the spring effort of spring I I to strike a blow" on thehead of the chuck 48 (see Fig. 13).

The valve, due to its inertia, and also under the influence of pressure in 20, continues down-- ward to seat onitsseat 49 on top of the chuck 48 (see Fig. 1a), thus completing the cycle.

When thecutter head 51 andcutters 61 are off bottom by elevation of the drill tubing, the

chuck 48 slides downward in the case I until thelower ring 50 seats on theseat 41 formed by thepin 44. The hammer 9- slides downward until thesplines 42 seat on theshoulder 43, thesplines 52 and 53 remaining in engagement. The distance between the shoulders and pin is such that the bottom of the hammer is above the top of the chuck. The valve is thus not seated on its the hammer the valve remains seated on itsseat 49 in the chuck; notwithstanding the spring is elongated by reason'of the upward movement of thehammer 9. It remains seated until the pin 33' has reached its upward limit of travel inslot 28 and when it contacts the top of the-slot the continued upward motion u-nseats the valve mechanically by lifting the valve stem. As soon as this pin has lifted the valve sufficiently to dis-- charge the pressure in case I through port Ell to a pressure somewhat less than the pressure originally present in the case when the hammer is seated on the chuck the spring immediately lifts the stem into therecess 20 and snaps thevalve 26 against its seat 4Ia, thus closing therecess 2! Immediately thereafter the valve is unseated by the pin, the pressure in the chambers I9 and 20 and in the case I is equalized, through theports 58 and 59, with the pressure in the annulus between the case and the bore hole wall whereupon the hammer immediately descends to strike.

As the hammer descends the valve descends with the hammer, due to its mechanical connection to the hammer, the valve remaining seated against its seat lla during the descent becauseof the tension. of thespring 24 When thehammer 9 strikes the top ofchuck 48 and is thus arrested in its motion. the valve and valve stem continue to descend under the influence of their inertial force until th valve is seated on its seat on the chuck, thus closing ofi theport 58. The cycle is thus completed. Connection between theport 58 and case I being out off, pressure rises in case I and the hammer may repeat its upward motion as described above. While the hammer thus repeatedly strikes the chuck to cause hammer blows on thecutter 6|, the drill pipe rotates case I. By reason of thescrew connection 44, case I rotates the drivingsection 45 and through the medium of the splines rotates the chuck and thus also rotates the cutter. The cutter thus not only cuts by hammer blows but also rotates and cuts by rotation, which is simultaneously caused by the operation of the rotary turntable and the circulation of flushing fluid.

One of the primary purposes for the use of drilling fluid is to clear the cuttings away from the cutter head and to elevate them to the surface. In order to obtain these desired ends it is necessaiy to have a certain velocity of the fluid through the cutter nozzles and a certain rate of flow of fluid in the annular space between the drilling tocl and the bore hole wall. This requirement is well understood in the drilling art.

In ordinary drilling practice, it is suflicient to establish the upward velocity of the drilling fluid in the annulus between th drill string and the bore hole by regulating the total pressure of the fluid entering the drill pipe, since the nozzle velocity thus obtained will be sufficient both to clear the cutters and to elevate the cuttings.

In the reciprocating hammer bits of my invention the discharge of fluid through the nozzles such as shown at 59 of Fig. 10, for any given hammer, depends on the length of stroke and the rate of reciprocation of the hammer, since this determines the length of time during which theport 58 is in communication with the interior of the case I and the pumping effect of the hammer. The fluid discharges through thenozzles 59 intermittently in spurts during the period when the hammer is falling. In some sizes of hammers and some depths of bores, and

depending on other conditions of drilling operations, this intermittent discharge may give a sufiicient rate of flow of fluid in the annulus to elevate the detritus. However, under other conditions and for other sizes of hammers and gauge of bores, it is found that this will give an insuflicient rate of flow oi drilling fluid to efficiently elevate the cuttings. In order to increase the velocity of the drilling fluid in the annulus between the tool and the bore hole wall without interfering with the operation of the hammer, I have provided an auxiliary circulation of drilling fluid which is substantially independent of the operation of the hammer. The fluid pressure inside the case I being at all times higher than the pressure in the annulus between the tool and the bore hole wall, fluid flows through ports I2 into the chamber II and through the chambers I4 and I 6,chamber 3, through theports 5 into said annulus outside the case. However, except when the hammer is elevated, the pressure inside case I is only slightly higher than the pressure in the annulus between the tool and the bore hole wall, the pressure being substantially equalized through theports 58 and 59. When the hammer and the valve are seated on the chuck and the hammer is elevated this differential pressure rises. The flow through ports I2 into chamber II, through I4 and I6, 3, andports 5, thus increases as the hammer is elevated. The rate of flow is adjusted by the proper selection of the size of the port openings to give the additionally desired rate of flow. Additional flexibility is provided to adjust this rate of discharge to varying conditions of operation by the provision of a replaceable choke I3 which may be changed by disassembly of the tool and the introduction of a choke of proper opening into its seat, as shown in Fig. 1.

It will be observed that this auxiliary fluid flow is by-passed away from theport 58. Since this fluid discharge, which is in addition to the fluid flow incident to the operations of the hammer, does not flow through theport 58 and thenozzles 59, it does not interfere with the discharge of the fluid used to operate the hammer and thus will not affect the rate of hammer reciprocation.

The circulation of fluid through theports 5 has the additional advantage of preventing the intrusion of cuttings from the bore hole into the hammer throughsuch breather ports 5. Due to the fact that the section I0 rises and falls in the chamber I6, a pumping action is occasioned. The absence of ports such as I2 would produce inside the chambers I6 and 3, upon the descent of the hammer, a pressure lower than the pressure in the annulus outside the case because upon the descent of the section III inside the chamber IS a lowering of pressure in the chamber I6 results and thus cuttings may intrude by a back flow of fluid through theports 5 into thechambers 3 and I6. The continuous upward circulation of fluid through 58 prevents this intrusion of cuttings by maintaining a slightly higher pressure in chambers I6 and 3 than in the annulus. This is aided by the circulation of fluid between the walls of the section II] and the walls of the chamber I6 due to the clearance I5. This circulation has the additional efiect of clearing this annulus and chambers I6 and 3 of any possible detritus and preventing wear between the sliding surfaces of IO and IS.

Thus this auxiliary flow prevents wear and aids in increasing the volume of flow of fluid to supplement the fluid discharge through thenozzles 59 and gives the desired upward velocity of fluid in annulus between the tool and the bore hole wall.

In order to avoid any shock transmitted to the depending hammer cylinder I6 produced by any deviation from verticality of the hammer which could in some circumstances cause rupture of the connection between the cylinder and the casing, I have provided guides for the hammer as illustrated bysplines 42. These guide the lower end of the hammer in the case I. I have also provided splines I positioned between the casing and the chamber I6. Thus, the hammer is constrained to move substantially concentrically of the case I except as deviation may be occasioned by the clearances which manufacturing tolerances require for the fit of thesplines 41 and by theclearances provided for at I5. Any deviation from verticality of the hammer thus remaining and resulting in any component of force against the walls of the cylinder I6 which results in shock blows is minimized and made harmless by reason of the splines I which thus constrain and hold the cylinder IS in the case I by a close fit therein to reduce and make harmless any such shocks.

the center line of the valve recess.

.As will be seen from Figs. lb, and 11 and 12, no portion of the valve or valve stem when the hammer and valve are off the chuck projects into thebore 58. Thus upon the elevation of the hammer and the withdrawal of the valve from its seat upon the chuck the pressure may be immediately discharged through the port without any restriction being imposed upon its fiow into theport 58. As will be seen from Figs. 1b., ll to 15, inclusive, as the hammer starts rising, the valve remaining on itsseat 49, the clearance between the seat Ma. and 26 becomes immediately enlarged, thus avoiding frictional contact between theseat 41a and thevalve body 26. When the hammer has reached its limit of upward travel the pressure is sufiiciently dissipated so that it may fall immediately. For many bore hole sizes the space restrictions, imposed by the requirement that the annulus between the bore .hole wall and the tool besumciently large to permit the desired volume of flow of fluid, impose severe restrictions upon the sizes of the parts and theport 53. The freeing of this port to per- .mitthe maximum rate of discharge of fluid from the case I through the port 5-3 is thus of importance.

In order to insure this result the valve has-been designed so that the valve stem is entirely within the recess provided therefor in the hammer. to

wit,recess 29, and the valve spring is positioned above the valve inrecess 19.

Provision is also made to insure that any-shocks imposed by the hammer upon the valve stem will not cause a fracturing thereof.

It will be recognized that ordinary manufacturing clearancesbetween thesplines 42 andthe case and the clearances which are provided at may permit the hammer to cantor-move axial- .ly to one side or the other of the chuck center line. If the bore hole is not exactly vertical, .as

.is usually the case, thesplines 42, on reciprocation in case -I, wil1,-on rotation of the drill .pipe, permit the hammer to cant or shift to the .low side-of the hole due to the vertical angle of deviation of the bore hole. be emphasized by the increase in clearance resulting from wear on continued use.

The spring tension will tend to keep the valve stem coaxial with .the hammer recess. If the :valvehad on-itsprevious descent not been seated L coaxially with theport 58 abend will be imposed on the valve stem. The ham-mer will upon the descent kick the valve .over. to be coaxial with If the hammer cants, the hammer and the valve on their descent may strike the chuck with the center lines of the chuck and hammer at a slight angle to each other. .As aresult-of the above circumstances severe bending forces are imposed on the valve .stem. This bending may be sufficient, unless provisions are made therefor, to cause a, fracture of the .valve stem. In order toavoid this I have provided for the following features in the valve stem-construction.

The-upperslotted portion of the valve stem is tapered as previously described. The taperedportion 32 provides for a greater clearance at the upper part of the valve stem than at 3| where it is in sliding contact. The other provision is a section of reduced diameter shown at 33. This portion is relatively morefiexible than the more rigid yoke portion. The tapered por- .tion of the valve stem permits the upper portion of the valve stem to have a'limited lateral move ment while maintaining normal sliding contact The degree of can-t will at 31. This will reduce flexure in the valve stem. There is provided suificient flexibility in the valve stem, particularly because of the reducedcross-sectional area 33, to permit some flexure. .As a result of this construction also the valve may seat on the chuck at an acute angle thereto without damage.

The tapers provided onthevalve body 26 and theseat 41a permit of the elevation of the ham- .mer while the valve is on itsseat 49 without .friction between the seat and the valve. As the valve enters the seat Ma, the upper frustoconical valve shoulder guides the valve to .its

correct concentric position with the hammer valve recesses 19 and 20 seating centrally of the seat Ma, as shown .inFigs. 121.12, and 13.

As has been previously described, as the ham- .mer strikes the chuck at high speeds it is accelerated both by gravity and the hammer spring. The valve is carried downwardly with the hammer .at the speed of .the hammer and when .the hammer strikes the chuck the valve projected downwardly due to the .inertia of the Valve and valve stem and the pressure inchamber 2 0. The valve therefore strikes itsseat 49 with considerable force. .Also when the valve is retracted to its seat Ala it strikes this seat with great force.

I provide a cushioning effect to prevent damage to the valve by reason of the blow thus struck. A blow struck by the valve either on its seating on the chuck at 49 or on its seat Ma. is cushioned by theresiliency of therubber ring 31. Instead of rubber .rings 1 may use any other resilient means such as flat coil springs as illustrated in 'Fig. .14.

.An additional hydraulic cushion is obtained to reduce the shock on the seating of theValve 26 on its .seat Ma. The seating of the valve occurs while the valve and hammer are both moving. The recesses I9 and 2.0 furnish achamber for entrapment of .fiuid. The fluid is forced out as the valve body is eased quickly to its seat on 4m. This is a form of hydraulic shock absorber.

The response of the hammer, that is, the speed .of striking and the force of blow of the harmner, .for any given hammer design, depends upon the speed of response of the valve. It is essential that when the valve is unseated by the arrival of the pin .30 at the top of theslot 28 the spring have .suflicient tension to immediately retract the valve in the recess to seat the valve against the frusto-conical seat Ma. Ifthe tension is too small the valve will have insufiicient average vertical acceleration and the valve will not be seated in its frusto-conical seat Ala at the time the hammer is ready to make its descent. The result will be that the valve will be out of phase with the motion of the hammer. This may not only reduce the speed of reciprocation of the hammer, but may cause damage to the valve. If the tension of the spring is too great the hammer on the upstroke unseats the valve before the hammer reaches top stroke, that is, the tension of the spring may be suflicient toeunseat the valve against the fluid pressure before the pin .30 has reached the uppermost position intheslot 28. This will have a tendency to shorten the stroke of the hammer.

By using an extension type spring instead of a compression type and by pinning the upper end of the valvestem to the lower endof the valve spring and the .upper end of the spring to the hammer by pins .38., as .described above, and by the provision of valve seat 4m .as described .above, I am able to fix the initial spring tension to a definite value commensurate with the weight of the valve and valve stem.

I can so fix the final tension of the spring when the hammer is elevated to overcome the pressure of the fluid exerted throughport 41 and prevent the Valve from being pumped downwardly during the descent of the hammer prior to the seating of the hammer.

When, as previously described, thevalve 25 is seated on its seat onchuck 48, the spring is designed so that this initial tension and the tension of the spring during its extension are not sufficient to unseat the valve until thepin 30 has reached its uppermost point of travel. Since the fluid pressure exerted throughport 4| is known and can be controlled by regulating the mud pump pressure at the top of the well, and since the dimensions of the various ports and other parts of this hammer are known, a spring may be designed by regulating the diameter of the wire and the number of coils so that the spring may have the desirable final and initial wnsions previously described.

During the portion of the travel of the hammer when thevalve 26 is on its seat on thechuck 48, the valve stem is retracted from therecesses 20 and I9, thus creating a zone of lower pressure. This pressure is relieved and pressure maintained in the valve chamber by means of the port 4] which permits fluid to enter from the higher pressure zone in the annulus of the case I into thechambers 20 and [9 This is necessary in order to maintain the pressure in the chambers l9 and 20 to hold the valve on its seat on the chuck until thepin 30 reaches its uppermost travel in theslot 28. In like manner when the valve stem is retracted by thespring 24, excess fluid is discharged through theport 4| into the annulus of the case as a result of the pumping action of this valve stem. Thebores 29 act as additional ports for the same purpose. Theslots 28a provided in the yoke of the valve stem permits fluid to pass between the valve stem and the walls of the recess and are made of sufficient diameter to pass any beet pulp, bagasse,

hay, cellophane, mud or other materials used in drilling fluids in oil field practice.

It is desirable, because of the variable hardness of the formation which must be drilled, to regulate the force of the blow of the hammer to be greater for harder formations and less for formations which are not as tough or are more brittle, as the case may be. By lengthening the stroke of the hammer I can increase the force of the blow and by diminishing the length of the stroke of the hammer I can reduce the force of the blow.

I have provided for this purpose a simple expedient for altering the stroke of the hammer by changing the position of thepin 30 in thebores 29. The hammer stroke may thus be increased in length or diminished in length. The force of the blow may therefore be predeter mined before the hammer is run to bottom for cutting of a hole in the formation. Thus by placing thepin 30 in anupper bore 29 the stroke of the hammer may be lengthened and by placing thepin 30 in alower bore 29 the hammer stroke may be shortened.

I have also provided means for controlling the initial and final spring tension of thespring 24 to be adjusted to the variation in the stroke length imposed by the positioning of thepin 30 as previously described. Thus, as will be seen from what has been said before, it is necessary to assure that the proper spring tensions exist at both ends of the stroke of the hammer in order to operate the valve properly. When the stroke is shortened, the initial spring tension, when the hammer is elevated, may not be sufficient to retract the valve into therecess 20 when thepin 30 reaches its uppermost position against the top of theslot 28. In such case when thepin 30 is elevated to anupper bore 29 thepin 23 is removed from thebore 2| at the top of the recess I9 and moved to a higher bore hole in order to increase the tension of the spring so that when thepin 30 reaches its topmost point of travel there will be sufficient tension in the spring to raise the valve. In like manner when the stroke is lengthened by moving thepin 30 to alower bore 29, the tension in thespring 24 caused by the upward movement of the hammer while the valve is seated on the chuck may create a tension in the spring sufficient to unseat the valve before the hammer has reached its uppermost point of travel and thepin 30 has reached its uppermost position in theslot 28. In such case thepin 23 is moved to alower bore 2| in order to reduce the tension on the spring so that the tension be not sufficient to unseat the valve until thepin 30 has reached the uppermost point of travel.

While I have described a particular embodiment of my invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

I claim:

1. A hammer type rotary rock drilling apparatus which comprises in combination a hammer case having at its head a joint adapted to be attached to the end of a string of rotary drill tubing through which flushing fluid is pumped downwardly, a hammer mounted for vertical reciprocation within a central tubular section forming a chamber inside said case, said hammer having at its top a head of reduced diameter, the head of said case having a bore open at the bottom and closed at its top except for ports connecting the interior thereof with the annular space between the case and the bore of the well; said bore forming a cylinder in which the reduced head of the hammer reciprocates with the latter acting as a. piston, a compression spring mounted in said bore bearing against said reduced head and tending to push said head down wardly in the tube, a passageway for flushing fluid in said head leading into said head at a point beneath said depending tube and then upwardly through said head into said bore, whereby the flushing fluid can pass from the central chamber of the case through the hammer head, through the bore and outwardly into the space between the case and the well bore, conduit means for passing flushing fluid from the drill tubing around said bore and into the central chamber of the case, the said hammer having sufficient clearance in said chamber to pass said fluid downwardly between the hammer and the case wall, a central bore at the bottom of said hammer, a reciprocating valve mounted at the bottom of said bore having a valve stem leading upwardly into said hammer bore, an extension spring attached between the top of the valve stem and an adjustable fastening means at the top of the hammer bore whereby the spring tends to pull the valve stem upwardly into said bore, means for limiting the downward motion of said valve 13 stem in said bore relative to the hammer, a chuck slidably mounted in the bottom of the case the top of'which forms an anvil to receive blows from said hammer, a cutting head attached to the lower end of the chuck, the chuck having a central bore connecting with ports in said cutter head to supply flushing fluid from the central chamber of the case to said cutting head, the top of the chuck forming a valve seat for said valve which when seated closes the central bore of said chuck and means providing relative longitudinal movement connecting the case and the chuck to rotate the chuck and hence the cutter head as the case is rotated by the retation of the drill tubing; said valve and hammer being so constructed and arranged that when said valve closes the central bore of the chuck the pressure of the flushing fluid in said central chamber forces the hammer upwardly off the chuck while the valve remains seated until said means for limiting the downward motion of the valve stem becomes operative, whereby the valve is then lifted and the resulting decrease in the pressure of the flushing fluid in the central chamber due to its flow through the central bore of the chuck coupled with the downward pressure of said compression spring at the top of the hammer causes the hammer to descend and to strike the chuck whereby the valve again becomes seated.

2. The drilling apparatus ofclaim 1 wherein the valve stem has an upper tapered section the lowest point of which makes a sliding fit with the bore of said hammer so as to provide limited oscillatory motion of the valve about said lowest point serving as a pivot.

3. The drilling apparatus ofclaim 2 wherein the valve stem is of reduced diameter between the lowest point of the tapered section and the valve to make the stem flexible,

4. The drilling apparatus ofclaim 1 wherein splines are provided between the lower end of the hammer and the wall of the case to guide the hammer in its reciprocating motion.

5. The drilling apparatus ofclaim 1 wherein means are provided for adjustably restricting the fluid passageway leading through the head of the hammer into said bore and from thence to the annular space between the case and the bore of the well.

6. The drilling apparatus ofclaim 1 wherein said means for limiting the downward motion of the valve stem relative to the hammer is adjustable vertically to provide valve strokes of adjustable length downwardly.

7. The drilling apparatus ofclaim 6 wherein the extension spring at the top of the valve stem is provided with an adjustable upper fastening means to change the tension on the spring and thereby to change the stroke of the hammer.

8. The drilling apparatus ofclaim 1 wherein the valve stem is connected to the valve body through resilient means which absorb the shocks caused by the valve striking its seat.

HARRY PENNINGTON.

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

UNITED STATES PATENTS Number Name Date 878,856 Beldiman Feb. 11, 1908 1,065,298 Currell June 17, 1913 1,695,452 Carnes Dec. 18, 1928 1,892,517 Pennington Dec. 27, 1932 2,312,290 Smith et a1 Feb. 23, 1943 2,344,725 Phipps Mar. 21, 1944 2,422,031 Merten June 10, 1947

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