US2187037A - Well tool or the like - Google Patents

Description

' L, H. KIRKPATRICK 2 187,037

WELL TOOL 0R THE LIKE Filed June 9, 1939 2 sheets-sheer 1 ,mamans n l lmnmmmlnuf' 'I Kx mi i N L. H. KIRKPATRICK WELL TOOL OR THE LIKE FiledrJune 9, 1939 2 sheets-sneer 2 #wir Patented Jan. 16, 1940 UNITED STATES PATENTI OFFICE 21 Claims.

This invention relates to oil well tools or the like such as rock bits, reamers, o-r any similar tools having rotatable cutters; and, incertain aspects, it more particularly relates to the bearing mountings of such cutters and improved means for lubricating the same. However, the bearing is of such nature that it may be utilized to advantage in any situation where it is to be submerged beneath fluid while in use, irrespective of the particular nature of the member which is supported for rotation, and therefore my claims are not to be considered as limited to particularities of supporting body or rotating members except when expressly speciiled. However, this broader aspect of the invention may be brought out advantageously in connection with a. description of the embodiment in an oil Well tool Where all service and fluid-pressure conditions are particularly severe. y

It has long been a serious problem properly to lubricate the cutters of oil well tools due to the extremely severe conditions to which such tools are subjected. For instance, the mud ladened circulating fluid (which is circulated downwardly through the tool and upwardly around the drill stem for the purpose of flushing the cutters and carrying the cuttings to the ground surface) is of anl abrasive nature and, unlessl prevented, enters into the bearing mountings of the cutters and abrades them to such extent that the useful life of the tool is of relatively short span. Efforts have been made in the past to lubricate such cutter bearings by providing an internal lubricant supply and isolating this supply from the well fluid by placing barriers at the ends of the bearings, the bearings, proper, being between barriers and h ence likewise protected from the well fluid. The barriers, however, hav-e heretofore been rigidly mounted upon the tool-carryingbody and, upon being subjected to extreme externally applied well pressure, they have distorted (due to the relatively low internal lubricant pressure opposing the inward buckling of the barriers), the distortion breaking the fluid seal and permitting free entrance of the abrasive circulating fluid to the lubricant and bearing surfaces.

An important object of the present invention is to provide a bearing structure which may be incorporated in, for instance, an earth boring l tool for rotatably supporting cutters or the like, and which may be lubricated from an internal 1ubricant supply and yet not be subject to the infiltration of well fluid under conditions such as spoken of above. A further object of the invention is to provide, in combination with b: rrier riers for sealing off the lubricant from the well fluid, the barriers being movable to adjust for variation in volume of the lubricant. The well fluid, of course, varies in pressure from one to l. hundreds of atmospheres, depending upon the depth of the well, and each time the tool is inserted into or withdrawn from a well of any ap` preciable depth, this great change in external pressure is imposed on the exposed sides of the pistons. Now all lubricants are compressible to some degree, and the change in volume resulting from such changes in external pressure which is imparted to the lubricant by the pistons, is considerable. My improved barriers readily trans- 25 mit the pressure of the well fluid to the lubricant and adjust themselves to variations in lubricant volume Without breaking the fluid seal.

The rigidly mounted 'barriers used heretofore, have failed largely because of their bodily irnmobility and hence their general inability to readily transmit to the lubricant the changes in pressure of the well fluid, it following that the barriers gave inwardly because of theradical pressure differential, allowing the fluid to pass the barriers in its attempt to equalize the pressure of the lubricant with that of the well fluid. 0f course, when the barriers or packing means were set up tight enough to withstand lthis external pressure, this leakage did not take place. However, when this was done, the friction resisting rotation of the cutters was too great and thus rendered the tool useless.

Other objects and features of the invention Will appear from the following detailed description, reference being had to the accompanying drawings, in which:

Fig. 1 is a side elevation of a typical reamer to which my invention has been applied;

Fig. 2 is an enlarged vertical section of one of the cutter assemblies taken as indicated on line 2-2 of Fig. 1; f

Fig. 3 is a horizontal section taken on line 3-3 of Fig. 2:

Fig. 4 is a view similar to Fig. 2, but showing a modified form of cutter bearing assembly;

Fig. 5 is a vertical section of a typical rock bit to which my invention is applied, the section being taken as indicated by line 5-5 of Fig. 6;

Fig. 6 is a vertical section taken on line 6 6 Aof Fig. 5;

Fig. 7 is an enlarged fragmentary section of one of the side cutter assemblies viewed in the same aspect as Fig. 5;

Fig. 8 is an enlarged detail section of one of the bottom cutter assemblies viewed in the same aspect as Fig. 6;

Fig. 9 is a view similar to Fig. 7 but showing a modified bearing arrangement; and

Fig. 10 is an enlarged, fragmentary detail of the seal shown in Fig. 9.

The reamer shown in Figs. 1 to 3, comprises a body I0 threadably engageable at II with a drill string lnot shown), and having coupled to its lower end a usual bit I2. The usual circulation passage I3 extends vertically through the tool.

Toothed cutters I4` typically three in number, are carried by the body and are partly received by body recesses I5. Above and below these recesses, the body is provided with bosses I6 and I1` respectively, which receive the end portions of xed shafts I8. Shafts I8 are held against rotation by being pinned at I9 at their upper ends to bosses I6, while their lower ends are provided with fiat surfaces engageable with complementary bores 2I in bosses I1. Cutters I4 are rotatably mounted on shafts I8 by means' of antifriction bearings comprising radial thrust roller bearings and end thrust ball bearings 26, the latter being received by annular ball race 21, provided in bore 28 of each cutter, and annular ball race 28 provided in fixed collar 30 on each shaft I8. Shafts I8 are provided with flanges 32 for the purpose of preventing axial displacement of roller bearings 25; while the opposed ends of the rollers abut collar 30.

Bore 28 of each cutter is at each end counterbored to provide upper and lower conical bores 35 and 36 and adjoining cylindric counterbore portions 31 and 38. The upper and lower counterbores, each made up of a conical and cylindrical bore, are generally designated by the reference numerals 39 and 40, respectively. Cylindric portions 31 and 38, of counterbores 39 and 40,

are adapted to receive with fluid-tight peripheral engagement barriers 43 and 44, respectively, the

barriers or pistons being in the form of rings surrounding shaft portions and having fluid tight peripheral engagement therewith. The barriers are preferablymade of a resilient material such as rubber-preferably a synthetic, oil resistant rubber-like composition. For reasons described below, the outer ends of the barriers may be provided with annular V- shaped grooves 45 and 46 and, if desired, may have complementary shaped wedge rings 41 and 48 applied thereto, respectively, said rings preferably being relatively rigid.

The otherwise unoccupied space in chamberv C within which lie shaft I8 and bearings 25 and` 26 (which chamber is defined by the walls of bores 28, counterbores 39 and 40, and the opposed v ends of barriers 43 and 44) is completely filled with lubricant, counterbores 35 and 36 serving as lubricant reservoirs. Accordingly, the bearing mountings of cutters I4 are completely lubricated of the barrier material.

and are isolated from the external well fluid by barriers 43 and 44.

In this connection it will be realized that between all bearing faces are usual bearing clearances which clearances (not indicated because of their relatively small dimension) receive a film of lubricant and may be considered broadly as a part of chamber C. In fact, in certain variations to be described, the roller bearings are omitted and the cutter and shaft have direct bearing, in which case, the clearances spoken of above form communication passageways between the bearing faces and the reservoirs.

The outer ends of the barriers, or the wedge rings applied thereto, are exposed to the well fluid and subjected to the pressure thereof. If the pressure of the well fluid exceeds that of the lubricant, the differential inv pressure will act upon the barriers tending to move them axially inwardly until these pressures are substantially equalized, the movement required being theoretically dependent upon the compressibility of the lubricant for any given change in pressure. The barriers, in the position illustrated in Fig. 2, substantially occupy the cylindric portions 31 and 3B of the counterbores and slightly enter the conical portions 35 and 36 of their respective counterbores. Accordingly, upon such 'inward axial movement of the barriers and the consequent increased wedging effect imposed by the conical walls on the peripheries of the barriers, the fluid sealing effect between the barriers and the counterbores and between the barriers and theshaft will be of steadily increasing effectiveness. The fluid seal of the barriers with the counterbores and shaft I8, is also increased in effectiveness by the wedging action of wedge rings 41 and 48 against the inclined walls of the barrier grooves.

The degree of capacity to bodily deformation of the barrier depends upon the durometer The more yielding the material, the greater will be its deformation under given pressure and its consequent capacity for increasing the effectiveness of the fluid seal, and the less will be the effect of abrasive material in the well fluid. For instance, such material tends to imbed itself in such relatively yieldable material, rather than lodging between the bearing faces and causing scoring, asin the case of less yielding materials. There is, however, a factor limiting the degree of allowable softness for this material, this factor being the friction tending to resist rotation of the cutters, which friction increases in value directly as the degree of deformability or degree of softness of the material increases, for with an increase in the degree of softness of the material, there is increased capacity for movement into the diminishing conical bore and if this movement is excessive, excessive frictional drag will be placed on the cutters. I have found that various synthetic rubber compositions such as Duprene" or Anchorite have a degree of yieldability permitting the described increased effectiveness of the seal without causing excessive friction.

The procedure for assembling each'cutter may be as follows. Shaft I8, together with its loosely assembled roller bearings 25, is inserted within bore 28 of the cutter, and end thrust ball bearings 26 are dropped through cutter bore I5 onto race 21. During assembly, the spaces between bearings 25 and 26 in bore 28, and the counterbores 39 and 40 are completely filled with lubrithe reception of barriers 43' and 44.

creasing the compressibility of the lubricant. Barriers 43 and 44 are then forced into their respective counterbores, displacing a corresponding mass of lubricant as they are entered, excess lubricant being forced out through bore 50 around the initially comparatively loosely fitting threaded plug 5|. When sufficient lubricant has been displaced to permit the full sealing of the barriers, the cutter chamber is' finally sealed off as by completely closing bore 50 with weld material 52.

As shown in Fig. 3, boss |1 comprises complemental parts 55 and 56 secured to the body by screws 51. With these parts removed, the cutter assembly may be applied to the body by first inserting the upper end of shaft I8 into bore 58 of boss I6 (upwardly from below). Part 56 is then rotated behind shaft IB and finally fixed in place by cap 55 which is secured to the body by screws 51.

A variational form of the bearing mounting of the cutters is shown in Fig. 4. Here the cutter I4' is journalled for rotation on shaft I8 which is secured at its ends to body bosses I6' and |1.

"Shaft |8' comprises upper shaft portion 60 and lower, relatively reduced shaft portion 6| con-A nected by a taper portion 6I', the cutter being mounted for rotation on said shaft portions 60 and 6| at 62 and 63, respectively. Intermediate bearing portions 62 and 63, the cutter is centrally recessed at 64 to provide a lubricant reservoir communicating at opposite ends with bearings 62 and 63, and, by way of ports 8| and`82, with counterbores 39 and 40', respectively, which latter form a part of the reservoir system. Each cutter, as before, is counterbored at each end for The counterbores 39 and 40', however, are in this 1nstance fully conical throughout their length, and barriers 43' and 44 are complem'entally formed with outer conical surfaces 61 and 68. The ends of the cutters may be further counterbored at 69 and 10 for ,the reception of barrier-retaining washers 1| and 12 which are force-fitted within said counterbores. 'I'heupward thrust of cutter I4 is taken by thrust washer 15 placed between washer 1| at the upper end of the cutter and boss I6'. i

The outer end of the barriers 43 and 44 are exposed to the well fluid pressure by ports 16 and 11 which open to the exterior of the tool and to the spaces between the barriers and washers 1|,12.

I may, for the purposes of facilitating assembly, provide cutter |4' with a small tapered bore 18 through which the lubricant may be bled during full seating of the barriers, the bore 18 thereafter being closed by tapered plug 19 and, if desired, positively sealed by welding as at 80.

In this case it will be seen that the usual bearing clearances (not indicated because .of their relatively small dimension) between shaft portions 60 and 6| and cutter portions 62 and 63, respectively, provide passageways which not only receive a lm of lubricant, for bearing purpose,

but also put the counterbores 39' and 40 in co'mmunication with each other, with recess 64 and with the bearing faces of shaft and cutter.

Figs. 5 to 8, inclusive, illustrate my invention as applied to a rock bit indicated at |00. The bit is shown with the usual threaded connections |0| for engagement with the usual drill string, not shown.

The tool comprises side cutters |02 and bottom cutters |03 and |04. The passages for mud circulation through the tool are indicated at |05. The side cutters are identical in construction, and it is to be understood that the description of the one shown in detail in Fig. 7 will apply to the other. Cutter |02 is rotatably mounted on shaft ||0 by means of roller bearings III. Shaft ||0 has threadably secured thereto at ||2 and ||3 flanged nuts ||4 and 5, the hub portions ||6 and ||1 thereof engaging the hub portions ||8 and ||9 of the cutter to prevent axial displacement thereof. Provided in the opposite ends of cutter |02 are annular grooves |22 and |23, each having a conical side wall |24 and acylindrical side wall |25. Cylindrical side walls |25 are substantially continuous with the peripheral surfaces of hubs ||6 and ||1.

Barriers and |3| are adapted to have fluidtight engagement with the peripheral surfaces of hubs ||6 and ||1 and with the conical walls |24 of annular recesses |22 and |23, respectively, the annuli |20 of the side cutter overlying said hub portions. The spaces defined by the walls of the annular recesses and the inner faces of barriers |30 and |3| constitute lubricant reservoirs which have communication with the, bearing surfaces via passageways 32 and |33.

The procedure of assembly of the side cutter may be as follows, the assembly of shaft, cutters, bearings and barriers being accomplished to form a unit which is then bodily applied to the bit body, it being understood that web |4| is not applied to the body or to the unit until after the unit is in the position of Fig. 7. Flange ||5 is lrst threaded on shaft ||0 and welded thereto as indicated at |36. Then barrier |3| is placed on hub ||1. Bearings and side cutter |02 are then applied to the shaft, lubricant having been placed within the annular grooves |22 and |23, passageways |32 and |33. and within the space surrounding bearings Flange ||4, having barrier |30 mounted on its hub ||6, is then threaded on the shaft until hub portions ||8 and ||3 of the cutter are confined between hub portions ||6 and ||1. During this operation, barriers |30 and |3| will have seated respectively against conical walls |24 of annular grooves |22 and |23, excess lubricant having escaped through the threaded connection at V| I2 which is finally sealed by welding material as at |35. 'Ihe assembled unit, so far described, is then .applied to the body of inserting shaft ||0 in leg-bore l |0a and welding the shaft to the leg |33 as at |40. Web |4|, to be later described, is then positioned as in Fig. 7 and welded to flange ||5 at ||5a.

Bottom cutters |03 and |04 are substantially identical in construction except for the fact that bottom cutter |04 is the longer of the two and extends to the axial center of the tool. Otherwise, the description of one will apply to the other. Mounted in body legs |50 and secured thereto as by Welding at |5| is a horizontal shaft |52 which extends through body web |4|. Cutter |04 is rotatably mounted on shaft |52 by means of roller bearings |53, Press-fitted into counterbores |54a provlded at the ends of the bore which presents annular bearing surface |54, are rollerbearing-retaining washers |55. The ends of the cutter are provided with conical counterbores |56 which receive annular pisto'n barriers |51 and serve as lubricant reservoirs, there being passaged communication at |58 with the bearing surfaces.

Counterborcs |56 and barriers |51 are substantially the same in arrangement and operation as described in connection with 'he similar elements of the reamer cutter shown in Fig. 4, and therefore the description pertaining thereto will also apply in this instance.

Assembly of the bottom cutters with the tool body may be as follows. Web |0| and cutters |03 and |04 are first mounted on shaft |52, the cutters being mounted for instance, in the manner described in connection with the assembly of the structure shown in Figs. 1 to 4. The cutter, shaft and web assembly is then thrust upwardly into position of Fig. 8, the shaft ends being entered in grooves |58 of body legs |50 and welded thereto, and nipple position |4|a of the web being entered in body bore |59 which may contain packing |5911.. Thereupon, caps |58a are welded to the shaft and to the body legs as at |5|, and web IH is welded at ||5a to flanges ||5 of the sidecutter assembly.

Circulatlon fluid pumped into circulation passage |05 from the drill string is discharged therefrom through ports |05a and |0511. Ports |05a are directed toward the side cutters so that the discharged fluid will flush said cutters. Port I05b communicates with nipple I4Ia and web ports |4|b, the latter extending downwardly through the web and around shaft |52 at opposite sides thereof. Fluid discharged from ports |4|a circulates at the well bottom to clean it of cuttings and to then carry the cuttings upwardly around the tool and to the ground surface.

The modified form of side cutter shown in Fig. 9 varies from the showing of Fig. 7 mainly in the shape of the counterbore, the shape of the barriers, and the omission of roller bearings Otherwise, the construction of this side cutter mounting is substantially the same as shown in Fig. '7 and unchanged parts will bear the same reference numerals as in Fig. '7.

In this form, the side cutter |02 is mounted for rotation directly upon shaft ||0, and is held from axial movement by engagement with hub portions H6' and of flanges ||4' and H5. The annular grooves |22' and |23' are bounded by cylindrical side walls |24' and |25', and side walls |25 are substantially continuous with the peripheral surfaces of hub portions H6' and H1'. Positioned between these last mentioned peripheral surfaces and side walls |24 of the annular grooves are piston barriers |60 which, in this instance, are provided with annular V-shaped grooves in their opposed ends at |6| and also in their outer ends at |62. The barriers are provided with these V-shaped surfaces in order that components of the pressural forces of thefluid acting theregainst may be directed radially and thus increase the effectiveness of the fluid seal for a given pressure.

Under certain circumstances. there may be a tendency for the barriers to move apart under increased internal lubricant pressure. For instance,

the fluid in certain wells is of exceedingly high temperature, the heat transmitted to the lubricant being sufilcient to expand the lubricant to an extent driving the barriers outwardly against the effective well pressure. In such an event, a given barrier is checked in its outward bodily movement bythe associated annular rib |10, there being such a r.b formed on each of the flanges ||4 and I5. Thereafter, the internal pressure is efiective to bend the peripheral edges |60a and |601) about rib |10 as a fulcrum in a manner tending to spread these edges apart and thus effecting a tighter seal.

While I have shown and described several embodiments of my invention, various changes in design, structure and arrangement may be made without departing from the spirit and scope of the appended claims.

I claim:

1. In a device adapted to be exposed to external fluid pressure, a supporting member, a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member, the bearing between elements being located inwardly from the ends thereof, there belng provided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of said bearing, a pair of annular pistons located one in each chamber and having fluid-tight peripheral t with both said elements, the inner end faces of said pistons defining one end of the associated chamber and the pistons being bodily movable axially yof the shaft and chambers, the outer end faces of said pistons being exposed in a manner to receive the force of external fluid pressure, there being a passageway putting the piston-defined chambers into communication one with the other, and a body of lubricant substantially lling said piston-defined chambers and passageway and in lubricating communication with said bearing.

2. In a device adapted to be exposed to external fluid pressure, a supporting member, a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member, the bearing between elements being located `inwardly from theends thereof, there being provided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of said bearing, a pair of radially compressible annular pistons located one in each chamber and having fluid-tight peripheral fit with both said elements. the inner end faces of said pistons defining one end of the associated chamber and the pistons being bodily movable axially of the shaft and chambers, the piston-defined chambers having conical portions which taper towards the center of the associated element, said pistons being adapted to be radially compressed as they are moved' bodily and axially through s'aid portions towards one another, the outer end faces of said pistons being exposed in a manner to receive the force of external fluid pressure, there being a passageway putting the piston-defined chambers into communication one with the other, and a body of lubricant substantially filling said piston-defined chambers and passageway and in lubricating communication with said bearing.

3. In a device adapted to be exposed to external fluid pressure. a supporting member. a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member the bearing between elements being located inwardly from the ends thereof. there being provided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of said bearing, a pair of radially resilient annular pistons located one in each chamber and having fluid-tight peripheral fit with both said elements, the inner end faces of said pistons defining one end of the associated chamber and the pistons being bodily movable axially of the shaft land chambers, the piston-defined chambers having conical portions which taper towards the center of the associated element, said pistons being adapted to be radially compressed as they are moved bodily and axially through said portions towards one another and to resiliently, radially expand as they are moved in an opposite direction through said portions, the outer end facesof said pistons being exposed in a manner to re`- ceive the force of external fluid pressure, there being a passageway putting the piston-defined chambers into communication one with the other, and a body of lubricant substantially filling said piston-defined chambers and passageway and in lubricating communication with said bearing.

4. In a device adapted to be exposed to external fluid pressure, a supporting member, a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member, the bearing between elements being located inwardly from the ends thereof, there being provided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of said bearing, there being an annular passageway between the elements and between the chambers, communication between chambers and between the chanibersand the bearing being provided via said passageway, a pair of annular pistons located one in each chamber and having fluid-tight peripheral flt with both said elements, the inner end faces of said pistons defining one end of the associated chamber and the pistons being bodily movable axially of the shaft and chambers, the outer end faces of vsaid pistons being exposed in a manner to receive the force of external fluid pressure, and a body of lubricant filling said piston-defined chambers and the passageway.

5. In a device adapted to be exposed to external fluid pressure, a supporting member, a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member, the bearing between elements being located inwardly from the ends thereof, there being provided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of said bearing, there being an annular passageway between the elements and between the chambers, anti-friction bearing elements in said passageway, communication between chambers and between the chambers and the bearing being provided via said passageway, a pair of annular pistons located one in each chamber land having fluid-tight peripheral fit withboth said elements, the inner end faces of said pistons defining one end of the associated chamber and the pistons being bodily movable axially of the shaft and chambers, the outer end faces of said pistons being exposed in a manner to receive the force of external fluid pressure, and a body of lubricant filling said piston-defined chambers and the otherwise unoccupied space within the passageway.

6. In a device adapted to be exposed to external fluid pressure, a supporting member, a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member, the bearing between .elements being located inwardly from the ends thereof, there being provided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of of said pistons being exposed ina manner to receive the force of external fluid pressure, and a body of lubricant fillingv said piston-defined chambers and the otherwise unoccupied space within the passageway.

7. In a device adapted to be exposed to external fluid pressure, a supporting member, a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member, the bearing between elements being located inwardly from the ends thereof, there being pro-vided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of said bearing, there being an annular passageway between the elements and extending from chamber to chamber, antifriction bearing elements in said passageway, communication between the chambers and the bearing being via the passageway, a pair of annular pistons located one in each chamber and having fluid-tight peripheral fit with both saidelements, the inner end faces of said pistons defining. one end of the associated chamber and the pistons being bodily movable axially of the shaft and chambers, the outer end faces of said pistons being exposed in a manner to receive the force of external fluid pressure, and a body of lubricant filling said piston-dened chambers and the otherwise unoccupied space within the passageway.

8. In a device adapted to be exposed to external fluid pressure, a supporting member, a shaft element and a rotatable element associated to have rotational bearing one on the other, one of the elements being connected to the supporting member, the bearing between elements being located inwardly from the ends thereof, there being provided a pair of annular chambers in one of the elements and coaxial with the shaft element, said chambers being located near opposite ends of said bearing, a pair of radially deformable annular pistons located one in each chamber and having fluid-tight peripheral flt with both said elements, the inner end faces of said pistons defining one end of the associated chamber and the pistons being bodily movable axially of the shaft and chambers, the outer end face of each piston having formed therein a substantially V-shaped annular groove, a pair of relatively rigid rings substantially complementary to and entered, one each, in said grooves, the outer end faces of said rings being exposed in a manner to receive the force of external fluid pressure, there being a passageway putting the piston-defined chambers into communication one with the other, and a body of lubricant substantially filling said piston-defined chambers and passageway and in lubricating communication with said bearing. y

9. In a device adapted to be exposed to external fluid pressure, a supporting member, a pair of Ielements having rotational bearing one with the other, one of said elements being connected to said supporting member, an'd means for maintaining lubricating fluid between the coacting bearing surfaces of said elements, said means comprising a pair of barrier members each having fluid sealing engagement with both of said elements, there being formed a lubricant space closed at its ends by the inner faces of said barriers and including a clearance space between the bearing surfaces, and a body of lubricating fluid conned within said space, the outer faces of said barrier members being exposed in a manner to receive the force of external fluid pressure, one of said barrier members having capacity for bodily movement relative to the other whereby the lubricant pressure is variable in accordance with variations of the external pressure.

10. In a device adapted to be exposed to external fluid pressure, a supporting member, a pair of elements having rotational bearing one with the other, one of said elements being connected to said supporting member, and means for maintaining lubricating fluid between the coacting bearing surfaces of said elements, said means comprising a pair `of barrier members each having fluid sealing engagement with both of said elements, there being formed a lubricant space closed at its ends by the inner faces of said barriers and including a clearance space between the bearing surfaces, a body of lubrieating fluid confined within said space, the outer faces of said barrier members being exposed in a mannervto receive the force of external fluid pressure, one of said barrier members having capacity for bodily movement relative to the other whereby the lubricant pressure is variable in accordance with variations of the external pressure, and means for increasing the effectiveness of the sealing engagement of the barriers with said elements by virtue of a variation in external fluid pressure.

11. In a device adapted to be exposed to external fluid pressure, a supporting member, a pair of elements having rotational bearing one with the other, one of said elements being connected to said supporting member, and means for maintaining lubricating fluid between the coacting bearing surfaces of said elements, said means comprising a pair of barrier members each having fluid sealing engagement with both of said elements, there being formed a lubricant space closed at its ends by the inner faces of said barriers and including a clearance space between the bearing surfaces, a body of lubricating fluid confined within said space, the outer faces of -said barrier members being exposed in a manner to receive the force of external fluid pressure, one of said barrier members having capacity for bodily movement relative to the other whereby the lubricant pressure is variable in accordance with variations of the external pressure, and means for increasing the effectiveness of the sealing engagement of the barriers with said elements by virtue of an increase in external fluid pressure.

12. In a device adapted to be exposed to external fluid pressure, a supporting member, a pair of elements having rotational bearing one with the other, one of said elements being connected to said supporting member, and means for maintaining lubricating fluid between the coacting bearing surfaces of said elements, said means comprising a pair of barrier members each having fluid sealing engagement with both of said elements, there being formed a lubricant vspace closed at its ends by the inner faces of said barriers and including a clearance space between the bearing surfaces, a body of lubricating fluid confined within said space, the outer faces of said barrier members being exposed in a manner to receive the force of external fluid pressure, one of said barrier members having capacity for bodily movement relative to the other whereby the lubricant pressure is variable in accordance with variations of the external pressure, and means for increasing the effectiveness of the sealing engagement of' the barriers with said elements by virtue of a variation in external fluid pressure, said means comprising a wedge surface on one of said elements engageable by said last mentioned barrier member in its bodily movement.

13. In a well tool adapted to be exposed to external fluid pressure, a body member, a shaft carried by said member and held against rotation with respect thereto, a cutter having rotational bearing on said shaft, and means for maintaining lubricating fluid between the bearing surfaces of said shaft and cutter, said means comprising a pair of annular piston barriers each encircling and having fluid sealing engagement with the shaft and being slidable with fluid sealing engagement through bores provided in the cutter at opposite ends of the bearing surfaces, said bores being in constant communication one with the other and with a clearance space' between the bearing surfaces, and a body of lubricating fluid confined within the clearance space by the inner ends of the piston barriers, said piston barriers being exposed at their outer ends in a manner to receive the force of external fluid pressure.

14. In a well tool adapted to be exposed to external fluid pressure, a body member, a shaft carried by said member and held against rotation with respect thereto, a cutter having rotational bearing on said shaft, and means for maintaining lubricating iluid between the bearing surfaces of said shaft and cutter, said means comprising a pair of annular piston barriers each encircling and having fluid sealing engagement with the shaft and being slidable with fluid sealing engagement through bores provided in the cutter at opposite ends of the bearing surfaces, said bores being inwardly tapered whereby to increase the effectiveness of the sealing engagement with said piston barriers upon movement of said piston barriers inwardly of said bores, said bores being in constant communication one with the other and with a clearance space between the bearing surfaces, and a body of lubricating fluid confined within the clearance space by the inner ends of the piston barriers, said piston barriers being exposed at their outer ends in a manner to receive the force of external fluid pressure.

15. In a well tool adapted to be exposed to external fluid pressure, a body member, a shaft carried by said member and held against rotation with respect thereto, a cutter having rotational bearing on said shaft, and means for maintaining lubricating fluid between the bearing surfaces of said shaft and cutter, said means comprising a pair of radially yieldable annular piston barriers .each encircling and having fluid sealing engagement with the shaft and being slidable with fluid sealing engagement through bores provided in the cutter at opposite ends of the bearing surfaces, said bores being in constant communication one with the other and with a clearance space between the bearing surfaces, and a body of lubricating t fluid confined within the clearance space by the inner ends of the piston barriers, said piston barriers being exposed at their outer ends in a manlner to receive the force of external fluid pressure.

16. In a well tool adapted to be exposed to external iiuid pressure, a body member, a shaft carried by said member and held against rotationA with respect thereto, a cutter having rotational bearing on said shaft, and means for maintaining lubricating iiuid between the bearing surfaces of said shaft and cutter, said means comprising a pair of radially yieldabley annular piston barriers each encircling and having fluid sealing engagement with the shaft and being axially movable withK the fluid sealing engagement in tapered bores provided in the cutter at opposite ends of the bearing surfaces, said bores being in constant communication one with the other and with a clearance space between the bearing surfaces, and a body of lubricating fluid conflned within the clearance space by the inner ends of the piston barriers, said piston -barriers being exposed at their outer ends in a manner to receive the force of external fluid pressure.

17. In a well tool adapted to be exposed to external uid pressure, a body member, a shaft carried by said member and held against rotation with respect thereto, a cutter having rotational bearing on said shaft, and means for maintaining lubricating fluid between the bearing surfaces of said shaft and cutter, said means comprising a pair of relatively axially movable annular piston barriers, each encircling the shaft and having fluid sealing engagement with the shaft and said cutter, there being formed by said shaft and cutter and between the inner ends of the piston barriers a closed lubricant space communicating with a clearance space between the bearing surfaces, and a body of lubricating uid within said spaces, said piston barriers being exposed at their outer ends in a manner to receive ythe force of external uid pressure.

of the cutter along the shaft, a pair of chambers sunk, one each, in opposite ends of the cutter and in communication with said space, and a pair of piston barriers provided one for each of said chambers and movable bodily axially therein.

19. In a well tool, a body member, a shaft carried by said member, a cutter having an axially extending bore adapted to take said shaft but of a diameter to provide an annular space between the shaft and the bore-wall, bearing elements in said annular space, means limiting the end play of the cutter along the shaft, a pair of annular chambers sunk, one each, in opposite ends of the cutter and in communication with said space, said chambers being coaxial with but radially spaced from said bore, and a pair of annular piston barriers provided one for each of said chambers and `movable bodily axially therein.

20. In a well tool, a body member, a shaft carried by said member, a cutter having an axially extending bore adapted to take said shaft but of a diameter to provide an annular space between the shaft and the borewall, bearing elements in said annular space, means limiting the end play of the cutter along the shaft, a pair of annular chambers sunk, one each, in opposite ends of the cutter and in communication with said space, said chambers being coaxial with but radially spaced from said bore, one of the peripheral walls of each of the chambers having a portion, at least, tapering with respect to the cutter axis to progressively decrease the radial extent of the chambers as their inner ends are approached, and a pair of annular piston barriers provided for each of 'said chambers and movable bodily axially therein.

21. In a well tool, a body member, a shaft carried by said member, a cutter having an axially extending bore adapted to take said shaft with bearing clearance, means limiting the end play of the cutter along. the shaft, a pair of annular chambers sunk, one each, in opposite ends of the cutter and in communication with the space developed by the bearing clearance, said chambers being coaxial with but radially spaced from said bore, and a pair of annular piston barriers provided one for each of said chambers and movable Vbodily axially therein.

LAFAYETTE H. ERKPATRICK.

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