US3065416A - Well apparatus - Google Patents

Description

Filed March 21, 1960 4 Sheets-Sheet l NOV. 20, 1962 1 D JETER 3,065,416

WELL APPARATUS Filed March 2l, 1960 4 Sheets-Sheet 2 NOV. 20, 1962 J, D JETER 3,065,416

WELL APPARATUS J f/a//y d@ fer JNVENToR.

BY 52W, M5 1 Pf United States Patent O 3,055,416 WELL AlTPARATUS John D. Jeter, Dallas, rllex., assigner to Dresser Industries, Inc., Dallas, Tex. Filed Mar. 21, 196i), Ser. No. 16,599 1S Claims. (Cl. 324-70) This invention relates to apparatus particularly useful in connection with determining the speed of drilling motors, such as turbodrills, employed in the drilling of wells. In one of its aspects, it relates to an apparatus for generating pulses or variations in pressure in a flowing drilling fluid and particularly to the generation of such pulses at a rate which is proportional to the speed of the drilling motor powered by the drilling iluid so that the flowing column of fluid in the well can be used to transmit these pulses to the earths surface.

It is known to use a iluid powered downhole motor, such as a turbodrill, to turn `a bit to drill a well. Usually such motors take the form of a turbine and hence their speed of rotation is dependent in large part upon the torque required to turn the bit. This torque, during a normal drilling operation, can vary over a wide range and hence .the speed of the turbine, if not controlled, can likewise vary over a wide range. In order that the drilling operation can proceed most satisfactorily, it is desirable that the driller be able to determine the speed of the downhole motor. The usual tachometers are not suitable for determining or measuring the speed of the motor. Thus, many of them would require mechanical or electrical connections extending from the motor to the earths surface. Obviously, this is not feasible. Also, special problems are involved due to downhole drilling conditions. Thus there are the problems of shock, pressure, heat and space limitations, all of which have thwarted previous attempts to provide a suitable tachometer for downhole use.

It is accordingly an object of this invention to provide a device suitable for use in connection with determining the speed of a downhole drilling motor, the device being especially adapted to operate the adverse conditions found in a bore hole and also to transmit the desired indication of speed to the earths surface without requiring any mechanical or electrical connection up the bore hole for transmitting such information.

Another object of the invention is to provide a device which will generate pressure pulses or variations in a column of ilowing drilling lluid at a rate which is proportional to the speed of the drilling motor so that these pulses can be sensed at the earths surface to indicate the speed of the motor.

Another object of the invention is to provide an apparatus of this general type for generating pressure pulses which tend to remain relatively constant in amplitude despite variation in the pressure and flow rate of the drilling lluid.

Another object of the invention is to provide a pulse generating apparatus such as for determining the speed of a downhole drilling motor in which apparatus the pulse width or time of duration can be readily adjusted.

Another object of the invention is to provide such an apparatus in which the less rugged of the mechanical elements are effectively sealed from the drilling lluid by a new arrangement of sealing elements which not only perform a sealing function but also prevent ambient pressures and changes thereof from substantially interfering with operation of the device.

Other objects, advantages and features of the invention will be apparent to one skilled in the art upon a consideration of the specification, vthe appended claims and the attached drawings wherein:

rf* ICS FIGS, 1A and 1B illustrate a preferred embodiment of the invention, it being understood that these views are continuations of one another;

FIG. 2 is a vertical half-section further illustrating the preferred control valve actuating mechanism shown on a smaller scale in FIGS. lA and 1B;

FIG. 3 is an enlarged half-section of pulse generating valve and the pressure responsive means for driving same, the Valve being illustrated in retracted or full open position;

FIG. 4 is a development showing one cycle of cam action for the cams illustrated in FIG. 2;

FlG. 5 is a diagram showing the motion relationships of the cam and the control valve;

FIG. 6 is a View taken on the line 6-6 of FIG. 1B; and

FIG. 7 illustrates in reduced scale a turbodrill having a motor of turbine type powered by drill fluid, disposed as a continuation of FIG. 1B downward.

Referring to the drawings, the illustrated tool generally includes a tubular housing or sub Il) adapted to be connected as a part of the drill string such as by being connected at its upper end to drill collar 11 and at its lower end to an adaptor l2 which in turn is connected to a turbodrill or other downhole motor. The pulse generating apparatus also includes a pulse generating valve means 13 in the housing actuatable to periodically restrict llow of the drilling iiuid through the housing to thereby generate pressure pulses or variations in the flowing drilling fluid. The pulse generating valve is shown as being actuated by a pressure responsive means 14 which causes the pulse generating valve to periodically move toward seated position to generate the pulses. The actuation of the pressure responsive means is in turn controlled by a control valve l5 which causes the pressure differential across the pressure responsive means to increase and decrease at a rate which is proportional to the speed at which rotatable member 16 is rotated by the turbodrill. Thus, from an overall operational viewpoint, the turbodrill drives -a rotatable member which causes the control valve to elect timed changes in pressure differential across the pressure responsive means so that the pulse generating valve periodically restricts ow in the column of drilling fluid to thereby generate pulses at a rate which is proportional to the speed of rotation of the turbodrill.

Turning now to a detailed description of the illustrated embodiment, the pulse generating valve means comprises an annular seat Z0 and a valve element 21 adapted to coact therewith to restrict ow through the housing. For a purpose to be made more clear hereinafter, the seat and valve element are so designed that even when the valve element is in full open position as shown in FIG. 3, a pressure drop will exist across the seat.

In order to reduce ythe likelihood of 4water hammer, one or more bypass grooves 22 can be cut in the seat orr in the valve element so that iluid can continue to llow even when the valve element is seated.

The valve element is mounted so as to be reciprocated toward and away from the seat by the pressure responsive means i4. The Valve mounting can take the form of a piston rod 23 slidably mounted in housing 24 and carrying a piston 25 at its lower end which is reciprocal in cylinder 26. The piston has its upper side constantly exposed via ports 27 to the pressure of iiuid downstream of seat 2l). Means are also provided for constantly exposing the lower face of the piston to pressure upstream of the seat. This means can comprise the hollow portion of piston rod 23 which communicates via passage 28 in the valve member with a valve element extension or dart 29. This dart contains a continuation of passage 28 and has a plurality of narrow slots 30. Slots 30 are made suiiiciently small so as to strain out sand and other particles in the drilling uid as the latter ows through the slots. The slots do not clog with these particles because the main body of drilling fluid flowing downwardly past the dart washes the particles away.

With the foregoing construction, it will be seen that with a pressure drop always em'sting across seat 20, and with the upper and lower sides of piston respectively constantly exposed to pressure of fluid downstream and upstream of the seat, the upstream pressure will tend to urge the valve element upwardly to restrict ow of duid. Then, as will be explained in greater detail, by periodically venting cylinder 26 to a point downstream of the seat, the valve element can be made to reciprocate in synchronism with the periodic venting. In this connection, it should be noted that the effective cross-sectional area of piston 25 is made larger than the eective area of orice 31 so that when cylinder 26 is not vented, the valve element will always be positively urged upwardly toward its seat.

Means are provided for limiting the upward force applied to valve element 2l by the pressure responsive means to not exceed a predetermined maximum value. Stated in another way, such means limits the pressure drop across seat 20, with valve element 2l. moving toward closed position, so that such drop can never exceed a predetermined maximum value. As a result, the amplitudes of the pulses generated in the owing iiuid stream by movement of valve element 2l toward its seat tend to remain at a relatively constant value despite variations in the fluid flow rate through the tool.

The means for accomplishing the foregoing includes a resilient means such as spring 32 having one end abutting a ring 33 carried by piston rod 23 and the other end abutting piston 25. Piston 25 is made slidable along the piston rod. Ihen by proper preloading of spring 32, the amount of upward force exerted by piston 2S will be limited by a value dependent upon the preloading of the spring and the loading rate of the spring. Thus, when differential is initially applied to piston 2,5', the piston, spring and piston rod will move upwardly as a unit. As this occurs, the differential across seat Ztl increases with the resultant increase in downward force tending to resist seating of valve element 2l. As soon as this downward force equals the force equivalent to the preloading of spring 32, piston 25 will begin sliding along the piston rod until it reaches stop 34. During this sliding movement, valve element 21 will move upwardly only enough to increase the differential across the valve element and hence the downward force applied to the valve element so as to offset the loading rate of spring 32, thereby keeping the seating and unseating forces balanced. Since the loading rate of the spring can be made small, the preloading of spring 32 can be made to determine the amplitude of the pulses generated.

It will be thus seen that the arrangement is such lthat a valve opening force applied by pressure differential across the seat is increased until it balances out a predetermined valve closing force applied by the pressure responsive means and that further movement of the pressure responsive means so as to tend to increase the valve closing force is not substantially gffective to increase the differential across the seat. The degree of valve closing will of course vary with the fluid ow rate in that at very high rates, a lesser degree of closing will be obtained than when the ow rates are lower whereby the pulse amplitudes tend to remain more constant with varying ow rates than would be the case where the pulse generating valve was fully closed irrespective of flow rate.

Means are provided for controlling the application of pressure differential to the pressure responsive means so as to cause the pulse generating valve to be actuated at a rate proportional to the speed of the turbodrill. Such means can be one for periodically venting cylinder 26 and hence the upstream pressure side of piston 25,

to a point downstream of seat 20 to thereby cause the alternate application of higher and lower pressure dilferentials to the pressure responsive means. The frequency of venting is proportional to the speed of the downhole motor, and therefore the actuation of the pulse generating valve i3 is likewise proportional to such speed. The venting means includes a control valve including a valve seat 35 having internal passage 36 communicating with cylinder 26. A valve element, such as ball 37, is carried by reciprocal valve head 33 so as to be alternately seated and unseated with respect to seat 3S. Thus reciprocation of head 38 periodically vents cylinder 26 to a point downstream of seat 26 via a passage 39.

Means are provided for causing the valve element (ball 37) to be cyclically seated and unseated at a rate which is proportional to the speed of the motor or turbodrill. Thus a shaft fili is provided at the lower end of the apparatus to be engaged by paddle 41 carried by a driver 42 connected to the turbine-shaft of the turbodrill (not shown). The upper end of shaft 40 drives a suitable reduction gear train 43 through an overrunning clutch 44. The purpose of the latter is to assure that the gear train and the mechanism thereabove can be driven in only one direction. The output of the gear train is connected to a lower one of a pair of barrel cams 45 and 46. The lower barrel cam 45 is rotatably mounted in housing 24 while the upper cam 46 is reciprocally mounted therein but is prevented from rotating by pin 47 riding in slot 48 in plunger 49, the latter being connected via an extension 5d to valve head 38.

Assurance that plunger 4% will not be rotated can be provided by a pin 5l riding in slot 52 in the plunger and carried by a bearing 53 ixed in the housing.

The interengaging faces -54 and 55 of the cams are formed so that as the lower cam 45 rotates, the upper cam 46 will be reciprocated as a cam follower. For example, the operating cams can be matched, symmetrical, axial-motion barrel cams with an instant one-quarter inch drop, l5 degree dwell, uniform one-quarter inch rise in degrees, a l5 degree dwell and an instant drop in that order. Thus referring to FIG. 4, which is a development of one cam cycle, it will be seen that cam follower 46 is gradually moved upwardly to seat ball 37 and then is rapidly retracted to unseat the ball.

With the foregoing arrangement, the rotative movement of the rotatable member 40 is converted into a reciprocal movement and the latter movement is ernployed to control venting of the pressure responsive means. The action of the mechanism is positive in that a known numerical relationship will exist between the number of times shaft 40 is rotated and the number of pulses generated under the control of the controlV or pilot valve 15. i

Means are provided for adjusting the duration of closure of the control valve during each cam cycle to thereby adjust the pulse width or duration while at the sarne time always assuring that the control valve will be positively seated. The adjustable means can be provided by threading seat 35 in body 14 so that the extent of time that ball 37 is in seated position during the cam cycle is adjustable. Thus by moving seat 35 upwardly, ball 37' will be seated during a smaller portion of the cam cycle and by moving the seat downwardly, the ball will be seated for a longer portion. The reason for this is, of course, that the cams have the capacity to move the ball a distance equal to D (FIG. 4). If the ball is seated earlier in the cycle of movement, it will remain seated for a longer portion of the cam cycle and vice versa.

A stop nut 56 can be provided to hold the seat in its adjusted position.

It is also contemplated that ball y37 can be made adjustable upwardly and downwardly to similarly control the pulse duration.

In order to permit the foregoing adjustment of the seat or ball and at the same time assure seating of the ball, without mechanically binding the mechanism, cam follower 46 is slidably disposed with respect to plunger 49 and is urged downwardly against a shoulder 57 on the plunger by spring 5S. The other end of .the spring abuts a ring 59 car-ried by the plunger 49. With this arrangement, it will be seen that the upper cam, spring and plunger 49 will travel upwardly as a unit during the initial portion `of the cam cycle until the motion is stopped by the ball seating as indicated at A in FIG. 5. Thereafter, cam follower 46 continues travelling upwardly compressing spring 58 until point B of the cycle (FIG. 5) is reached at which time the cam follower is retracted into engagement with shoulder 57 and the entire cam follower, plunger and ball assembly move rapidly downwardly under the inuence of spring 67. The distance between points A and B determines the pulse width and since the position of point A can be adjusted along the sloping portion of the curve of FIG. 5 by adjusting valve seat 35, the pulse width can be adjusted.

FIG. 7 illustrates a conventional turbodrill powered by well uid introduced through drill string 10. The turbodrill comprises a housing l2 adapted to be attached to drill string 10 as a continuation thereof and contains a turbine type motor designated generally as N92, turning on a shaft 101 which carries member 42 at its upper end. A bit 1013 powered by the turbine rotates in relation to housing l2. in response to flow of drilling fluid through the turbine. rI`ur-bodrills, including a drill bit and a -motor of turbine type driven by circulating well iluid, are old and well known. They are illustrated, described and listed for sale in the Composite Catalogue of Oil Field Equipment and Services, 1960-61 edition, published by 'World Oil, of Houston, Texas, at pages 3478 and 4844. Since the present invention is not limited to any particular type of fluid driven turbine or motor, it is believed unnecessary to describe the motor further.

Referring now to FIGS. 1B and 6, it will be seen that the rotable member in the form of shaft 40 has its upper end coaxial with housing 24, while its lower portion is curved outwardly so that the lower end of the shaft lies laterally of the housing axis. As shown in FIG. 6i, the arrangement is such that a plane containing the axis of shaft 40 also contains the axis of housing 24 as well as the axis of the turbodrill. Paddle 4l is displaced laterally from this plane and is parallel thereto so that it applies force to turn the shaft at a right angle to the above-mentioned plane. This arrangement minimizes application of force which would tend to urge the shaft radially of the housing or turbodrill.

Means are provided for effectively sealing the overrunning clutch, gear reduction train, and cams in a fluid-tight housing. Thus, the lower end of the housing is sealed to shaft 4t) by means of a flexible sleeve 60. The upper end of the sleeve is sealed to a bearing 61 which is tixed to housing 24. The lower end of the sleeve is sealed to a bearing 62 on the lower end of shaft 46B. A Wear ring 63, which may be of rubber or the like, is secured to the flexible sleeve for contact with paddle 41. It will be noted that the lower end of the sleeve effects a seal with the head of the bearing at 64 and that the wear ring extends down over the head of the bearing 62 to provide a further seal at 65. With this arrangement, the iiexible sleeve is closed over the end of the shaft. The sliding action occurs between the sleeve closing bearing and the shaft and between the wear ring and the paddle, but the sliding surfaces do not extend from the interior to exterior of the seal.

The other end of the housing is sealed by what may be termed a hydrostatic compensator. This device incl-udes a bellows 66 having one end sealed to housing 24 and the other end to valve head 38. This bellows will expand and contract to allow for ambient pressure changes so that the total pressures outside and inside of the sealed housing are the same. Thus the expansion and contraction of the fluid inside the sealed housing, high ambient pressures and the reciprocation of plunger 49 and extension 5@ do not cause any appreciable pressure differentials.

It is believed that the operation of the device is apparent from the foregoing and hence only a brief description thereof will be given.

As the turbodrill is rotated, shaft 4t) is rotated at a corresponding speed. The shaft speed is reduced in gear reduction train 43 with the result that lower cam 45 turns at a. relatively slower speed. As this cam turns, it causes cam follower 46 to reciprocate. The cam follower, spring 53 and plunger 49 move upwardly as a unit until the ball 37 is seated after which the cam follower continues its upward movement or over-travel. The resulting closure of the control valve f5 causes pressure in cylinder 26 to increase thereby driving piston Z5 upwardly to move the valve element 2li upwardly to restrict flow of fluid through orice 3l. Then upon further rotation of cam 45, cam follower 46 is permitted to drop downwardly, aided by spring 67, to open a control valve which exhausts cylinder 26 to a point below seat 26. This permits the pulse generating valve to open.

The series of pulses generated by the pulse generating valve are transmitted as pressure waves up the owing column of fluid in the drill string. These pulses can be detected by suitable equipment at the surface of the earth, such as with a microphone or the like, and then by suitable instrumentation known to the art, converted into an indication of the lr.p.m. of the turbodrill.

From the foregoing it will be seen that this invention is one wel-l adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments rnay be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed l. An apparatus for generating pressure pulses or Variations in a owing drilling fluid at a rate which is a function ofthe speed of a rotating motor powered by the drilling fluid which comprises, in combination, a tubular housing adapted to be connected as a part of a drill string, a motor connected to said drill string and powered by drilling fluid introduced through said drill string, valve means in the housing actuatable to periodically restrict tlow through the housing to thereby generate said pressure pulses in the owing drilling fluid, a member rotatably mounted in the housing and adapted to be engaged and driven by said motor at a speed proportional to that of the motor, and means connecting the rotatable member to said valve means and causing actuation of latter as aforesaid at a rate which is proportional to the speed of rotation of the rotatable member.

2. An apparatus for generating pressure pulses or variations in drilling fluid owing through a drill string, the pulses being generated at a rate which is a function of the rotative speed of a motor powered by the drilling fluid which comprises, in combination, a tubular housing adapted to be connected as a part of said drilling string, a motor connected to said drilling string and powered by ow of drilling tluid introduced through said drilling string, valve means in the housing including a valve element movable relative to a seat to periodically and at least partially restrict flow through the housing to thereby generate said pressure pulses in the owing drilling fluid, pressure responsive means connected to the valve element and having opposite sides respectively constantly exposed to pressure fluid from upstream and from downstream of said seat, means for periodically venting the upstream pressure side of the pressure responsive means to a point downstream of the seat to thereby cause the periodic application of a sufficiently large pressure differential to said pressure responsive means to cause it to move said valve element, a member rotatably mounted in the housing and adapted to be engaged and driven by said motor at a speed proportional to that of the motor, and means con necting the rotatable member to said venting means and causing the latter to vent said upstream side of the pressure responsive means at a rate proportional to the speed of rotation of the rotatable member.

3. An apparatus for generating pressure pulses or variations in a llowing drilling iluid at a rate which is a function of the rotative speed of a motor powered by the drilling iluid which comprises, in combination, a tubular housing adapted to be connected as a part of a drill string, a motor connected to said drill string and powered by ilow of drilling fluid introduced through the drill string, an annular valve seat in the housing, a Valve element reciprocal with respect to the seat to effect a variation in flow therethrough to thereby generate pressure pulses in the flowing drilling fluid, a cylinder in the housing, a piston in the cylinder and connected to the valve element to reciprocate the same, said piston being of larger effective area than the area of the valve element within said seat and having one side constantly exposed to :tluid upstream of said seat so that the piston is urged thereby to move the valve element toward said seat, a pilot valve lluidly connected to the cylinder and operable to periodically vent said one side of the piston to a point downstream of the seat, a shaft rotatably mounted in the housing, means for connecting the shaft to said motor so as to rotate the shaft at a speed proportional to that of the motor, and means connecting the shaft to said pilot valve and causing the latter to vent said cylinder at a rate which is proportional to the speed of rotation of said shaft.

4. An apparatus for generating pressure pulses or variations in drilling fluid flowing through a drill string, said pulses being generated at a rate which is a function of the rotative speed of a motor powered by the drilling fluid which comprises, in combination, a tubular housing adapted to be connected as a part of said drill string, a motor connected to said drill string and powered by llow of drilling iluid introduced through the drill string, an annular valve seat defining a portion of the passageway through the tubular housing, a valve element mounted for reciprocation toward and away from the seat, pressure responsive means connected to the valve element to reciprocate the same responsive to changes in pressure differentials across the pressure responsive means and including means extending through the seat to provide a tluid passageway from upstream of the seat to a side of the pressure responsive means such that upstream pressure can act on the pressure responsive means t urge the valve element toward said seat, means for venting said side of the pressure responsive means to a point downstream of the seat to thereby cause alternate application of high and low pressure differentials to the pressure responsive means to cause it to reciprocate said valve element, a member rotatably mounted in the housing and adapted to be engaged and driven by said motor at a speed proportional to that of the motor, and means connecting the rotatable member to said venting means and causing actuation of the latter as aforesaid at a rate which is proportional to the rotational speed of the rotatable member.

5. The apparatus of claim 4 wherein the pressure re sponsive means is movable relative to the valve element and wherein its connection to the valve element includes a force transmitting resilient means limiting the effective force applied by the pressure responsive means to move the valve element to be not greater than a predetermined maximum value whereby variations in the rate of flow of lluid through the apparatus do not cause a corresponding variation in the amplitude of `the pulses being generated.

6. The apparatus of claim 5 wherein the pressure responsive means is a piston in a cylinder and slidable on a piston rod connected to the valve element, and said resilient means being a preloaded spring between the piston and rod causing the piston and rod and valve element to initially move as a unit and then permitting the piston to slide along the rod thereby limiting the force applicable by the piston to the rod and hence to the valve element.

7. An apparatus for generating pressure pulses or variations in drilling fluid flowing through a drill string, the pulses being generated at a rate which is a function of the rotative speed of a motor powered by the drilling fluid which comprises, in combination, a tubular housing adapted to be connected as a part of the drill string, a motor connected to said drill string and powered by llow of drilling iluid through vthe drill string, valve means in the housing including a main Valve element movable relative to a main valve seat to periodically restrict llow through the housing to thereby generate pressure pulses in the flowing drilling fluid, pressure responsive means connected to the main valve element and having opposite sides respectively exposed to pressure fluid from upstream and from downstream of said main valve seat, means including a control valve seat providing fluid communication between the upstream pressure side of the pressure responsive means and a point downstream of the main valve seat, a control valve element mounted in the housing to reciprocate toward and away from said control valve seat to periodically restrict ilow therethrough, a rotatable member rotatably mounted in the housing and adapted to be engaged and driven by said motor at a speed proportional to that of the motor, and means connecting the rotatable member to the control valve element and converting rotary motion of the rotatable member to a reciprocatory motion for moving the control valve element.

8` The apparatus of claim 7 wherein one of the control valve seat and element are adjustable axially relative to the other so that the duration of the pressure pulse can be adjusted.

9. The apparatus of claim 8 wherein the means connecting the rotatable member to the control valve element includes interengaging cam elements, one of which is connected to the rotatable member to be rotated thereby and the other of which is fixed against rotation but reciprocal in the housing and connected to the control valve elements to reciprocate the same, the contour of the cam elements being such that rotation of one causes recprocation of the other.

10. 'the apparatus of claim 9 wherein one of the connections to the cam elements includes a preloaded resilient means arranged to permit the cam element to overtravel after the control valve element has seated whereby the adjustment of the pulse duration time can be made as aforesaid and yet the control valve element will always close.

11. The apparatus of claim 7 wherein the means connecting the rotatable member to the control valve element is disposed in the Huid-tight housing, the control valve element being at one end of such housing and having a fluid-tight seal therewith, and wherein said rotatable member is a shaftV having one portion coaxial with said housing and another portion curving so that one end of the shaft is disposed laterally of the housing axis, a flexible sleeve having one end sealingly xed to the housing and the other end extending to thesaid one end of the shaft, a cap-type bearing sealed inside said other end of the flexible sleeve and having an imperforate portion extending across said one end of said shaft.

y12. An apparatus for generating pressure pulses or variations in a llowing drilling fluid which comprises, in combination, a housing adapted to be made up as a part of a tubular well string, a motor connected to said well string and powered by well fluid introduced through the well string, valve means in the housing including a valve element movable toward and away from seated position with respect to a seat to periodically restrict flow through the housing to thereby generate Said pulses in said flowing drilling fluid, and closing means for periodically applying a closing force to move the valve element toward its seat by overcoming the opening force of the flowing fluid tending to move the valve element away from its seat including means for transmitting such closing force to the valve element until the closing and opening forces are balanced and thereafter maintaining the forces in balance despite the tendency of the closing means to increase the force applied to close the valve means so that the valve element can automatically adjust its degree of closure with the valve seat in accordance with the rate of drilling fluid flow to thereby produce pulses having an amplitude which varies substantially less than the variation of ow rate through the valve means.

13. The apparatus of claim 12 wherein the closing means includes a pressure responsive means connected to the valve element and exposed to pressure of said drilling fluid to generate said closing force, the connection to the valve element including a resilient means through which the closing force is transmitted to the valve element.

14. The apparatus of claim 13 wherein the pressure responsive means is a piston movable relative to the Valve element and said resilient means is a preloaded spring connecting between the piston and valve element.

15. An apparatus for generating pressure pulses or variations in a flowing drilling fluid which comprises, in combination, a housing adapted to be made up as a part of a tubular well string, a motor connected to said well string and powered by flow of well fluid introduced through the well string, valve means in the housing actuatable to periodically restrict flow through the housing to thereby generate said pulses, pressure responsive means connected to the valve means and operable to actuate the valve means as aforesaid responsive to increasing and decreasing the pressure differential across the pressure responsive means, and means for controlling said pressure differential including a control valve seat communicating one side of the pressure responsive means with a pressure source such that flow through the seat will change the differential across the pressure responsive means, a control valve element movable between open and closed positions with respect to said seat, means capable of applying a force to move the valve element a predetermined distance within the limits of which the element is seated, and means for adjusting the point at which the valve element becomes seated during the lapplication of seating force thereto so that the duration of restriction of flow by the valve means can thereby be adjusted to determine the pulse width or duration.

16. The apparatus of claim 15 wherein said control valve element is reciprocal between seated and unseated positions and wherein said means capable of applying a closing force to said control valve element in a cam follower having a resilient connection to the element so that the follower can move the element to seated position and thereafter overtravel to continue its movement, a cam driving said follower through its movement, and drive means for moving the cam responsive to rotation of a rotatable member.

17. The apparatus of claim 16 wherein said adjusting means is provided by mounting one of the control valve element and seat so that the distance therebetween, when the control valve is in full open position, can be changed.

18. The apparatus of claim 17 wherein said cam and cam follower are barrel cams, one of which is rotated by the drive means and the other is xed against rot-ation but is reciprocal responsive to rotation of said one cam, and a spring connecting said other cam to the valve element, said spring being preloaded so that the valve element and said other cam move as a unit to seat the valve element and thereafter said other carn continues its movement by compressing the spring thereby allowing said other cam to overtravel.

References Cited in the le of this patent UNITED STATES PATENTS 2,494,183 Lincoln Jan. 10, 1950

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