US2814463A - Expansible drill bit with indicator - Google Patents

Description

Nov. .26, 1957. w, KAMMERER, JR 2,814,463

EXPANSIBLE DRILL BIT WITH INDICATOR Filed Aug. 25, 1954 2 Shets-Sheet 1 IN V EN TOR.

Aer/v52 W K/IMMEEEE, r12.

I47TORNEY- i I x I 1957 A. w. KAMMERER, JR 2,814,463

EXPANSIBLE DRILL BIT WITH INDICATOR Filed Aug. 25, 1954 v 2 Sheets-Sheet 2 F I F2104 g2;-Q 87 82 9; r I 7 84 as 83 f1? 2 x 7 Q4 I 40 I 95 i5 9 Z4? 9.! I I I 17 I34 I 18x 4 i I HE K4 4 5259, TIQ.

United States Patent Qfice 2,814,453 Patented Nov. 25, 1957 EXPANSIBLE DRILL an" WITH INDICATOR Archer W. Kammerer, In, Fullerton, Califl, assignor, by

direct and mesne assignments, to Rotary Oil Tool Company, Huntington Park, Califi, a corporation of California Application August 25, 1954, Serial No. 452,185

18 Claims. (Cl. 255-76) The present invention relates to rotary drill bits of the expansible type, which are capable of being run through strings of well casing, and of drilling or enlarging bore holes below the casing to a greater diameter than the inside diameter of the casing.

Rotary drill bits of the above-identified type have cutters which are initially retracted during lowering of the bit through the well casing, the cutters being expanded outwardly after the bit has been located below the casing. Usually, the drill bit is merely rotated until its cutters have been expanded outwardly, to form an annular shoulder in the wall of the bore hole, after which drilling weight is imposed on the bit and the latter progressively lowered as the drilling operation proceeds, to enlarge the hole along the required length.

Heretofore, the operator had no assurance or indication that the cutters were expanded outwardly to their maximum extent before imposing drilling weight on the rotary bit. As a result, an undersized hole would be produced in the event the cutters were not fully expanded. Moreover, in relatively soft formations, the drill bit might not drill or ream a cylindrical hole. Instead, the cutters would produce rifling grooves in the side wall of the hole.

When using expansible drill bits for enlarging bore holes drilled through relatively hard formations, a comparatively large force is required to expand the cutters outwardly to their maximum extent against the resistance offered by the hard formation. Certain types of expansi-" ble drill bits pump drilling fluid down the drill pipe and through the bit, the flow through the bit being restricted to produce a back pressure operable to expand the cutters outwardly. The restriction to fluid flow through the bit cannot be too great in view of the necessity for pumping adequate drilling fluid through the bit to flush the cuttings from the drilling zone and carry them to the top of the hole. As a result, the back pressure that can be built up is limited, correspondingly limiting the expansion force imposed on the cutters and available to penetrate the latter into hard formations.

Accordingly, it is an object of the present invention to provide an expansible drill bit which gives a sensible indication to the operator that the bit cutters have been expanded outwardly to substantially their fullest extent. By virtue of such indication, the operator is assured that a full annular shoulder has been produced in the formation on which the cutters can operate.

Another object of the invention is to provide a subsurface bore hole tool having initially retracted parts that are to be expanded outward, in which outward expansion of the parts to substantially their fullest extent provides an indication to the operator at the top of the hole of that fact.

2 operation to insure the proper flushing of formation cuttings from the region of drilling to the top of the bore hole.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure l is a longitudinal section through an embodiment of the invention disposed in a well bore, with the cutters and other parts in their initial and retracted positions;

Fig. 2 is a longitudinal section, similar to Fig. 1, disclosing the cutters locked in their fully expanded positions;

Fig. 3 is an enlarged fragmentary section disclosing a portion of the apparatus, with the parts occupying the same positions as shown in Fig. l;

Fig, 4 is a view similar to Fig. 3, with the parts occupying the same positions as shown in Fig. 2;

Fig. 5 is a cross-section taken along theline 5--5 on Fig. 2;

Fig. 6 is a cross-section taken along the line 6-6 on Fig. 4. l The form of invention shown in the drawings includes a rotary expansible drill bit A, which can be secured to the lower end of the string of drill pipe B extending to the top of the well bore C, and by means of which the drill bit is lowered through a string of well casing D to a region below its casing shoe, where the hole enlarging operation is to commence. The general type of expansible drill bit shown in the drawings is both illustrated and described in Patent No. 2,545,036, to which attention is invited for certain structural details that are not disclosed nor described herein in detail.

The upper portion of the rotary drill bit consists of a mandrel 10having anupper pin 11 threadedly connected to asub 12 forming the lower end of the string A further object of the invention is to provide a rotary of drilling fluidthrough the drill bit during the drilling of drill pipe B. This mandrel includes anupper 'kelly ordrill stem member 13 slidably splined to themain body 14 of the drill bit. Theexterior 15 of the power portion of the kelly is non-circular or hexagonal in shape, being telescopically received in a companion non-circular orhexagonal socket 16 formed in themain bit body 14. The hexagonalkelly exterior 15 andcompanion socket 16 form a slidable connection between these parts, enabling the kelly 13 to be moved longitudinally with respect to thebody 14, while being capable of transmitting rotary movement to the body.

Themandrel 10 has a limited range of longitudinal movement within thebody 14, its downward movement being determined by engagement of thelower end 17 of the kelly with an inwardly directedbody shoulder 18, and its upward movement being limited by engagement of an external shoulder orpiston portion 19 of the kelly, fitting within acounterbore 60 in the body of the tool above itshexagonal socket 16, with one ormore stop rings 20 that may be of the split type. These stop rings are inserted within aninternal groove 21 in the upper portion 14a of the main body of the bit, the stop rings extending into a confinedcylindrical space 22 formed between the kelly ordrill stem 13 and thebody 14 of the tool.

Thetool body 14 has a plurality of expansible parts mounted on it. These includecutter supporting members 23 pivotally mounted inbody slots 24 onhinge pins 25 suitably secured to the body. Eachcutter supporting member 23 depends from ahinge pin 25, terminating in abearing supporting pin 26 inclined inwardly and downwardly. Aside roller cutter 27 is rotably mounted on each bearing supportingpin 26, being mounted on anti-friction roller andball bearing elements 28, 29 rollable on the bearing supporting pin. The ball bearingelements 29 lock thecutter 27 against endwise movement on thebearing supporting pin 26, as well as transmitting axial and radial thrusts between the cutter and supporting pin. The roller bearingelements 28 transmit primarily radial thrusts between these parts. The manner of mounting the ball and roller bearingelements 29, 28 between thecutter 27 and bearing supportingpin 26, and of retaining them in place, is specifically described in the above-mentioned Patent 2,545,036.

Thecutter supporting members 23 and thecutters 27 mounted thereon tend to occupy a retracted position substantially and entirely within the confines of themain body 14 of the bit. These cutter supporting members and cutters are expandible outwardly, to enlarge the size of the well bore C and to operate upon a formation shoulder E that the cutters produce in the latter. To accomplish the expansion, eachcutter supporting member 23 has aninclined expander surface 30 on itsinner portion 31 below thehinge pin 25 which tapers in a downward and inward direction. Eachexpander surface 30 terminatesina lock surface 32 formed on alock portion 33 of the cutter supporting member. -The outward expansion is accomplished by producing relative longitudinal movement between the mandrel l and thebit body 14, which will produce corresponding relative longitudinal movement between thecutter supporting members 23 and thetubular member 34 of the mandrel. Thistubular member 34 includes a lower portion;35 slidable within aguide 36 secured to thebody 14 and extending across the slotted region of the body below the lock.portions 33.

Located initially substantially above theguide 36 and below the hingepin 25 vand incutter member recesses 37 is a mandrel lock and expander 38 having outer surfaces 39adapted to engage theexpander surfaces 30 and thelock surfaces 32. The lock andexpander 38 may be formed integrally with thetubular member 34, the upper end of the latter being piloted within asocket 40 in the lower portion of thekelly 13. An enlargedboss 41 on the tubular member engages a downwardly facing shoulder-42 of the kelly, the tubular member being held against this shoulder by a suitable split retainer or lookring 43 snapped into aninternal groove 44 encompassing thekelly socket 40 and engaging a downwardly directedshoulder 45 formed on thetubular member boss 41. Leakage between theboss 41 and the Wall of the kelly Socket is prevent by asuitable side seal 51, in the form of a rubber 0 ring, disposed within agroove 52 in the boss and engaging the wall of thesocket 40.

The kelly 13 has acentral fluid passage 46 therethrough communicating with the string of drill pipe B. Fluid pumped through thispassage 46 can pass into an alignedcentral passage 47 in thetubular member 34,,

whereby drilling mud or similar drilling fluid can be pumped down through the tool for the purpose of removing the cuttings from the well bore C and flush them upwardly around the drill pipe B to the top of the hole.

Assuming that thebody 14 of the tool is elevated relatively along thetubular mandrel 10, the inclined expander surfaces 30 of thecutter supporting members 23 will be shifted upwardly along the lock andexpander portion 38 of the tubular member. During such up- .ward shifting, thecutter supporting members 23, and

thecutters 27 carried thereby, may be pivoted about the hinge pins 25 and urged in an outward direction. The

movement of thebody 14 with respect to thetubular mandrel 10 can continue until thecutters 27 have been shifted outwardly to their fullest extent, as determined by engagement of stop shoulders 53 on the cutter supporting members with companion shoulders 54 formed in the body on opposite sides of eachbody slot 24. When such engagement occurs, thelower end 17 of the kelly portion of thetubular mandrel 10 will engage thebody shoulder 18, and the lock andexpander 38 on thetubular member 34 will be disposed behind and in engagement with thelock portions 33 on thecutter supporting members 23.

It is to be noted that thesurfaces 32 of the lock portions on thecutter supporting members 23 and the companion surfaces 39 on the lock andexpander portion 38 of the tubular member are substantially parallel to the axis of the drill bit, to prevent the reactive forces of the formation on thecutters 27 from moving the latter inwardly. As a practical matter, it is preferred that the coengaging lock surfaces 32, 39 be inclined slightly in a downward direction toward the axis of the tool, to insure release of the lock andexpander portion 38 from thecutter supporting members 23 when the latter and thecutters 27 are to be shifted back to their retracted positions.

The relative longitudinal movement between thetubular mandrel 10 and thebody 14 of the tool, for effecting outward expansion of thecutters 27, is accomplished hydraulically. Thecounterbore 60 receiving thepiston 19 of thedrill stem member 13 is formed in the upper portion 14:: of the body, which actually constitutes a cylinder having acylindrical wall 61 extending from alower shoulder 62, defining the bottom of thecounterbore 60, to an upper head and guide 63 which had a dependingportion 64 inserted in the upper end of the cylinder 14a and releasably retained therein by asplit snap ring 65 carried in a groove in thecylinder head portion 64 and adapted to. be received within a generally V-shapedinternal groove 66 in the upper portion of the cylinder wall. Thehead 63, with thesnap ring 65 mounted in its groove, need merely be forced into the cylinder 14a, and, when located opposite the V-shapedgroove 66, the snap ring will expand inherently partially into the latter, to releasably lock thecylinder head 63 to the cylinder 14a.

The confinedcylinder space 22 is formed between thepiston portion 19 of thekelly 13, the periphery of the kelly above the piston, and the cylinder 14a. To provide this space, a suitable packing orside seal structure 67 is disposed in a suitablepiston ring groove 68 formed in the piston, which is adapted to slidably seal against thecylindrical wall 61 of the cylinder 14a. Fluid is thereby prevented from passing in a downward direction between thepiston 19 and the cylinder 14a. Similarly, fluid is prevented from passing in an upward direction out of theannular cylinder space 22 by a cylindrical packing or sealingstructure 69 secured to the cylinder 14a and slidably engaging the periphery of thekelly 13. This structure may take any suitable form. As shown, it consists of a lowerpacking supporting ring 70 resting upon asplit retainer ring 71 located within aninternal groove 72 in the cylinder 14a. A non-metallic packing 73 of any suitable material, rests upon thering 70, its upper end engaging anupper packing ring 74 hearing against asplit retainer ring 75 received within aninternal groove 76 in the cylinder 14a. The upper and lower split rings 75, 71 prevent substantial move ment of the packing structure with respect to the bit body cylinder 14a, thenon-metallic packing portion 73 of the sealingstructure 69 engaging thecylinder wall 61 to prevent leakage therealong and also slidably sealing against the peripheryof thedrill stem portion 13 of thetubular mandrel 10.

Fluid under pressure in the stringof drill pipe B and Within the tubular mandrel can be fed into the cylinder s ace 2'2throu'gh one ormore side ports 77 extending the tool in an upward direction with respect to thetubular mandrel 10, and correspondingly elevate the cutterj supporting members 23 andcutters 27 with respect to the "lock andexpander portion 38 of thetubular member 34 and expand thecutters 27 to their fullest extent.

As disclosed in the drawings, the restriction in the fluid flow through thetubular member 34, to build up the above-described back pressure, can be accomplished by providing thepassage 47 through the tubular.member 34 with a substantially lesser diameter than the diameter of thepassage 46 through thekelly portion 13 of the mandrel thereabove. In the present instance, the back pressure that can be developed is further increased by the provision of an indicator valve orflow restricting member 80 in thetubular mandrel 10.

'As disclosed, thisindicator valve 80 is adapted to slide along thewall 81 of thekelly passage 46, having a lower downwardly tapering portion 82 adapted to engage and seal against a companion downwardly tapering portion 83' formed at the upper end of thetubular member 34. When such engagement occurs, leakage along the tapered surfaces is prevented by a suitable annular gasket 84 provided in agroove 85 in the tapered portion 82 of the indicator member, which sealingly engages against the taperedsurface 83 of the tubular member.

- Theflow restricting member 80 has a central orifice orpassage 86 therethrough, that is of substantially less diameter and area than thepassage 47 through thetubular member 34, and, of course, much less than the area through thekelly passage 46 When theflow restricting member 80 sealingly engages thetubular member 34, a much greater back pressure'can be built up in thekelly 13, this pressure being imposed on the fluid in theports 77 and thecylinder space 22 to exert a greater relative lifting force on thebody 14 of the tool and on the cutter supporting'rn'embers'23 and exert a much greater outward expansion force on thecutters 27, forcing them into the wall of the formation, to insure the cutting of the proper shoulder E in the formation during rotation of'the drill pipe B, thetubular mandrel 10 and thebody 14 of the tool.

The relatively small size orifice orpassage 86 through the flow'restrictingmember 80 is effective in securing a great outward expansive force on thecutters 27 during their expansion to their maximum extent. Thereafter, it is desired that the flow of fluid through the tool A not be restricted to as great an extent. Accordingly, after thecutters 27 have been expanded outwardly to their maximum extent, it is desired to allow a greater flow of fluid down through thetubular member 34, for discharge through the lower end of the latter. Accordingly, provision is made for elevating the fiow restrictingmember orvalve 80 above itscompanion seat 83, to allow fluid to flow through thecentral orifice 86 and also through additional orby-pass passages 87 extending longitudinally through the flow restricting member and arcuately spaced from one another circumferentially around the latter. It is evident that the elevation of theflow restricting member 80 above itscompanion seat 83 will allow fluid to through the orifice 8 6 and also through the by-pass flgw passages as well. Such flow of fluid through a combined passage area that is much greater than the areathrough thecentral orifice 86 alone will result in a drop the back pressure in thekelly passage 46, as well (Figs. 1 and 3).

as in the drill pipe B for the same volumetric rate of flow'of fluid through the apparatus. i i

The elevation of the flow restricting member is accomplis'hed "when thecutters 27 have been expanded outwardly to substantially their maximum extent. Such elevation will'not only provide for the flow of a greater quantityof circulating fluid through the tool, but it will also provide an indication to the operator at the top of the hole that the cutters have been expanded outwardly to substantially their maximum extent.

The foregoingp'urposes are accomplished in the apparatus disclosed in the drawings by providing one or morelongitudinal bores 88through'the kelly portion 13 of the mandrel and extending from its lower end'17 into thepassage 46 throughthe' kelly at the location of theflow restricting member 80. Anactuating rod 89 is slidably mounted in each bore 88, this rod extending from the upper end of thebore 88 and initially projecting to a predetermined extent but of the bore below thelower end 17 of thekelly portion 13 of thetubular mandrel 10. Therod 89 is urged and retained initially in a position in which itsupper end 90 is disposed at the lower end of thekelly passage 46, itslower end 91 projecting partly below thelower end 17 of the kelly, by ahelical spring 92 located in alower counterbore 93. The upper end of the spring engages ashoulder 94 at the upper end of thecounterbore 93, its lower end engaging aflange 95 formed on therod 89. The extent of downward movement of eachrod 89 within thebore 88 is limited by engagern'ent of therod flange 95 with astop ring 96, in the form offa split retainer ring, received within agroove 97 in the kelly surrounding thecounterbore 93. Leakage of fluid along therod 89 is prevented by asuitable seal ring 98 inarod groove 99 slid-ably and sealingly engaging the wall of thebore 88.

Thesprings 92 normally retain therods 89 in their downward position, which will allow theflow restricting member 80 to shift downwardly into sealing engagement with the uppertapered end 83 of thetubular member 34. When the'body 14 of the tool has been elevated to its fullest extent with respect to thetubular mandrel 10, thelower end 17 of the kelly will engage thebody shoulder 18. Just prior to such engagement, thelower end 91 of eachrod 89 will engage thebody shoulder 18 and the rod will be shifted upwardly withinthe kelly bore 88, to engage and 'shift theflow restricting member 80 in an up ward direction a substantial distance above itscompanion seat 83. Snch'action will allow fluid to flow through thecentral orifice 86 in the flow restricting member, as well as through the by-pass passages 87 provided therein around the flow restricting orifice. The drop in pressure at the top of the well bore will advise the operator (who need merely observe the indications on a pressure gauge) that thecutters 27 have been expanded outwardly to the maximum extent, inasmuch as theflow restricting member 80 is elevated from itsseat 83 only as a result of thecutters 27 having been shifted outwardly substantially to their maximum condition.

The rotary expansible drill bit A shown in the drawings is lowered through the well casing D by means of the string of drill pipeB, with thecutter supporting members 23 and thecutters 27 in their initial retracted positions, and with therods 89 in their lower positions, the lower ends 91 of the latter projecting downwardly a predetermined distance below thelower end 17 of thekelly 13 The flow restricting and indicatingmember 80 may shift upwardly in thekelly passage 46 during lowering of the tool through the well casing, but the extent of its shifting is limited by its engaging asplit stop ring 100 provided in agroove 101 in thekelly 13 at itspin end 11. The drill pipe B can automatically fill with the fluid in the well casing D and well bore C by flowing upwardly through thetubular member passage 47 into thekelly passage 46, and through theflow restricting orifice 86 and .pipe thereabove.

of fluid flow through the apparatus, is, built up in thekelly'passage 46, this'fluid under pressure passing through theside ports 77 into thecylinder space 22, to elevate the cylinder portion 14a of the body, as well as theentire body 14 and thecutter supporting members 23 andcutters 27, with respect to thetubular mandrel 10. During such upward movement, the expander surfaces of thecutter supporting members 23 are brought to bear against the lock andexpander portion 38 of the mandrel, thecutters 27 being urged in an outward direction against the wall of the well bore C. The drill pipe B and'rotary drillbit A are rotated at the proper speed while fluid is being pumped through the apparatus, thecutters 27 enlarging the well bore without the drill pipe being moved vertically and drilling weight being imposed on the tool.

As thecutters 27 enlarge the well bore, the hydraulic force acting upon the body14 elevates it to a greater extent with respect to themandrel 10 and moves thebody shoulder 18 toward thelower end 17 of the kelly:

and thevalve actuating rod 89. Immediately prior to outward expansion-of thecutters 27 to their fullest extent, thebody shoulder 18 will engage the rods 89and shift them upwardly within thekelly 13 against the force of thespring 92, the upper ends 90 of the rods engaging theflow restricting member 80 and shifting it from itsseat 83. When thecutters 27 are expanded to their fullest extent, thelower end 17 of the kelly will engage thebody shoulder 18 and therods 89 will have been shifted upwardly to their maximum extent, to elevate the flow restricting member 80 a substantial distance above itscompanion seat 83 at the upper end of thetubular member 34, and also above the lower kelly shoulder 105 at the end of thekelly fluid passage 46.

When theflow restricting member 80 has been elevated above itscompanion seat 83, the fluid pressure will drop and the pressure gauge at the top of the well bore will advise the operator of that fact. When the fluid pressure drops, the operator knows that thecutters 27 have been expanded outwardly to their maximum extent. Accordingly, he will then impose downweight on the drill pipe B and themandrel 10, this downweight being transmitted through the drill pipe B and through the apparatus A, since the effective passage area through the tool has been increased as a result of the elevation of theindicator valve 80 above itscompanion seat 83 in themandrel 10. As a matter of fact, the combined area through thecentral orifice 86 and the by-pass passages 87 therearound may be made equal to or greater than the area of thepassage 47 through thetubular member 34, so as to avoid any material restriction to the flow of circulating fluid through the tool. Adequate circulation fluid can be pumped through the apparatus, after thecutters 27 have 'been expanded outwardly to the maximum extent, to in- "sure the proper flushing of the cuttings from the well bore to the top of the hole.

After the hole has been enlarged to the proper extent,

. or the cutters have'become worn, it'is desired to'retrieye the apparatus 7 from the well bore. The'pum'ps are stopped and the drill ;pipe B raised. The initial action 'will be a corresponding elevation of themandrel 10 with respect to the body14, to remove theexpander'and lock portion 38 of the mandrel above the lock and expander surfaces 30, 32' on'theYcutter supporting members 23, allowing the latter toshift back to retracted position within the confines of thebody 14. 4 The upward movement of themandrel 10 withrespectto body 14 is limited by engagement of the "piston 19 with the lower set of stop rings 20. Suchupward movement also raises thelower end 17 of the kelly above thebody shoulder 18 and allows thesprings 92, to reshift thevalve operating rods 89 back to their initial position,*such as disclosed in Figs. 1 and 3, whereupon the flow restricting-member or indicator valve can drop back into engagement with itscompanion seat 83. However, it is-immaterial that the flowof fluid through the apparatus is restricted to that permitted by the central orifice'86 through the indicator valve, inasmuch assuch orifice is of suflicient size to permit the drill jpipeB to drain during its elevation with the tool A through the well;bore C and the well casing D.

It is, therefore, apparent that a rotary expansible drill bit hasibeen provided, in which a positive indication is 'given to thefoperator of the full outward expansion of the cutters; Asaresult, he is assured of the production of a fulljformation shoulder E before imposing downweight on the tool, which will also insure the drilling of a truly cylindrical enlarged hole of the required diameter. When drilling in soft formations, the fact of outward expansion of the cutters to their maximum extent, before downweight or drilling weight is imposed on the apparatus A, will, insure the provision of a maximum shoulder to support thecutters 27, and thereby minimize "the tendency of the cutters to produce a rifiing action in the well bore C during rotation of the tool and its lowering in the hole. In the event that the apparatus is being used in relatively hard formations, thevalve indicating mechanism 80 incorporated in the apparatus will insure the provision of a'greater hydraulic expansion force for insuring the full outward expansion of the cutters, than would be present in the absence of the indicating device.

The inventor claims:

1. In a rotary well drilling bit for operation in a well bore: a main body; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; means movable downwardly relative to said body and said cutter means for expanding said cutter means laterally outward of said body; and means movable relative to said expanding means in response to downward movement of said expanding means to a position substantially fully expanding said cutter means outwardly for providing an indication of substantially full cutter expansion that can be sensed at the top of the well bore.

2. In a rotary well drilling bit for operation in a well bore; a main body; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; means for expanding said cutter means laterally outward of said body; and means on and movable with respect to said expanding means and engageable with means fixed with respect to said body upon substantially full outward expansion of said cutter means for providing an indication ofsuch substantially full outward cutter expansion capable of being sensed at the top of the well bore.

3. In a rotary Well drilling bit for operation in a well bore: a main body; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; said body having a central fluid passage provided with a fluid outlet within said body from which drilling fluid is adapted to discharge into the body and the well bore adjacent said cutter means; means for expanding said cutter means laterally outward of body; means for determining the pressure of fluid insaid passage; and means operable upon outzvard'expansion of said cutter means to shift said determining means to change the fluid pressure in said passage.

4. In a rotary well drilling bit for operation in a well bore: a main body; cutter means mounted on said body tor expansion from a retracted position laterally outward of said body; means providing .a central fluid passage in said body extending along said cutter means; means for expanding said cutter means laterally outward of said body; a device in said passage to restrict flow of fluid in' tha t portion of said passage extending along said cutter 'm eans; and means operable upon outward expansion or said cutter means for shifting said device to a position allowing greater flow of fluid in said passage portion.

"S /In a rotary well drilling bit for operation in a well boref'a mainbody having a central fluid passage; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; means for expanding said cutter means laterally outward of said body; a device in said passage having a central flow restricting passage for reducing flow of fluid in said central fluid passage below said device; and means operable upon outward expansion of said cutter' means for shi ft ing said device to a position allowing fluid to by-pass around said central flow restricting passage and flow at a. greater rate into said central fluid passage below said device.

6. In a rotary well drilling bit for operation in a well bore: .a main body having a central fluid passage; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; means for expanding said cutter means laterally outward of said body; a device in said passage having a plurality of flow passages communicable with said body passage below said device, said device being adapted to occupy a position in said body passage in which at least one of said flow passages is closed; and means operable upon outward expansion of said cutter means for shifting said device to a position opening said closed flow passage.

7. In a rotary well drilling bit for operation in a well bore: a main body having a fluid passage; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; means above said cutter means and responsive to the pressure of fluid in said passage for expanding said cutter means laterally outward of said body; means for determining the pressure of fluid in said passage; and means operable upon outward expansion of said cutter means to shift said determining means relative to said expanding means to a position decreasing the fluid pressure in said passage.

8. In a rotary well drilling bit for operation in a well bore: a main body having a fluid pasage; cutter means mounted on said body for expansion from a retracted. position laterally outward of said body; means above said cutter means and responsive to the pressure of fluid in said passage for expanding said cutter means laterally outward of said body; a device in said passage to restrict flow of fluid therein and cause pressure to be built up in said passage above said device to operate said expanding means; and means operable upon outward expansion of said cutter means for shifting said device to a position allowing greater fiow of fluid in said passage.

9. In a rotary well drilling bit for operation in a well bore: a main body having a fluid passage; cutter means mounted on said body for expansion from a retracted po sition laterally outward of said body; means above said cutter means and responsive to the pressure of fluid in said passage for expanding said cutter means laterally out ward of said body; a device in said passage having a flow restricting passage to cause pressure to be built up in said passage above said device .to operate said expanding means; and means operable upon outward expansion ofi said cutter means for shifting said device to a position allowing fluid "to by-pass around said flow restricting passage. I 10. In a rotary well drilling bit for operation in a Well bore: a main body havinga fluid passage; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; means above said cutter means :and responsive to the pressure of fluid in said passage for expanding said cutter means laterally outward of said body; means for determining the pressure of fluid in said passage; and means on said expanding means engageable with means on said body upon substantially full outward expansion of said cutter means for shifting'said determining means to a position allowing greater flow of fluid in said passage.

11. In a rotary well drilling bit for operation in a well bore: a main body; cutter means mounted on and carried by said body for expansion laterally outward of said body; means for expanding and holding said cutter means outwardly of said body, including a mandrel connectible to a drill string"and-slidably splined to said body, whereby drilling torque is transmit-ted from said mandrel to said body; andrneans operable by said mandrel upon longitudinal shifting of said mandrel with respect to said body for providing an indication capable of being sensed at the top of the well bore that the cutter means has been expanded laterally outward.

12. In-a rotary well drilling bit for operation in a well bore: I a main body; cutter means mounted on and carriedby said body for expansion laterally outward of said body; means for expanding and holding said cutter means outwardly of said body; including a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to r said body, said mandrel having a fluid passage; means for determining the pressure of fluid in said passage; and means operated by said mandrel upon downward shifting of said mandrel with respect to said body to shift said determining means to a position changing the fluid pressure in said passage.

13. In a rotary well drilling bit for operation in a well bore: a main body; cutter means mounted on and carried by said body for expansion laterally outward of said body; means for expanding and holding said cutter means outwardly of said body, including a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body; and means carried by said mandrel and engageable with said body, upon longitudinal movement of said mandrel with respect to said body, to be shifted by said body relative to said mandrel to provide an indication capable of being sensed at the top of the well bore that the cutter means has been expanded.

14. In a rotary well drilling bit for operation in a well bore: a main body; cutter means mounted on and carried by said body for expansion laterally outward of said body; means for expanding and holding said cutter means outwardly of said body, including a mandrel connectible to a drill string and slidably splined to said body, whereby drilling torque is transmitted from said mandrel to said body, said mandrel having a fluid passage; means for determining the pressure of fluid in said passage; and means carried by said mandrel and engageable with said body, upon downward movement of said mandrel with respect to said body, to be shifted by said body to shift said determining means to a position changing the fluid pressure in said passage.

15. In a rotary well drilling bit for operation in a well bore: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body, said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; hydraulically operable means on said body subject to the pressure of fluid with respect to said mandrel to cause said expandermeans ;to expand said cutter meansrlaterally outward; means in said passage for determining the pressure of fluid in said passage; and means responsive to elevation of said body 'with respect to said mandrel for shifting said determining means to a position changing the fluid pressure in said passage.

16. In a rotary well drilling bit for operation in aiwell bore: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body, said mandrel having a fluid passage communicating with the drill string; coengageable expander means ,on said mandrel and cutter means; hydraulically operable means on said body subject to the pressure of fluid ,in said passage to elevate said body and cutter means with "respect to said mandrel to cause said expander means to expand said cutter means laterally outward; a device in 1 saidpassagc to restrict flow of fluid therein to enable fluid pressure to be built up in said passage; and means responsive to elevation of said body with respect to said fmandrel for shifting said device in said passage to a position allowing greater flow of fluid in said passage.

17. In a rotary well drilling bitfor operation in a well bore: a main body; cutter means mounted on said body for expansion laterally outward of said body; a mandrel connectible to a drill string and slidably splined to said body, said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; hydraulically oper- .2 a a 12 a Iable, means on said body subject to the pressure of fluid injsaid passage to elevate said body and cutter means ,with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; a device in said mandrel passage having a plurality of flow passages, said device being adapted to occupy a position in said mandrel passage in which at least one of said flow passages is closed;and means responsive to elevation'of said body with respect to said mandrel for shifting said device in said mandrel passage to a position opening said closed flow passage.

18. In a rotary well drilling bit for operation in a well bore: a main body; cutter means mounted on said body for expansion from a retracted position laterally outward of said body; means for expanding said cutter means laterally outward of said body, said expanding means having a fluid passage; means in said passage for determining the pressure of fluid in said passage; and means operable upon outward expansion of said cutter means to shift said determining means to change the fluid pressure in said passage.

References Cited in the file of this patent UNITED STATES PATENTS 1,611,282 Samuelson Dec. 21, 1926 1,900,226 Conant Mar. 7, 1933 2,699,921 Garrison Jan. 18, 1955 FOREIGN PATENTS 378,227 France Aug. 3, 1907

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