US1656436A - Underreamer - Google Patents

Description

Jan. 17, 1928. 1,656,436

A. G. HEGGEM UNDERREAMER Filed Jan. 16. 1922 s sheets-shane Jan. 11, 192s.

1 1,656,436 A. G. HEGGEM UNDERREAMER Filed Jan. 16, 1922 5 Sheets-Sheet 3 l f V/ /W/(ness Patented Jan. 17,1928.

l 1 ,6s6,436 PATENT OFFICE..

Amann o. miaou, or runen, ommen UNnnnnnmnn..

`Application Med January 16, 1922. Serial No. 529,650.

My invention relates to underreamers for drilling wells, and while in certain aspects it isvespecially directed to the production of ing a single `large and rugged bit capable of drilling straight ahead and coincidently performing an underreamin operation, there are other aspects of t e invention which may be advantageously applied to the well known type of underreamers having a pair of expanding bitsor cutters, examples of this latter type of underreamers being disclosed in Patents No. 748,054, granted to Edward Double' December 29, 1903, and No. 827 ,595, granted to Elihu C. Wilson July 31, 1906.

The principal ob]ect.of the invention is to provide an underreamer in which'the`cut'- ting means thereof may automatically assume drillin position when the tool issues through the ottom of a well casing and in which, upon the underreamer passing out of the top of the casing, the cutting means will automatically remain in a positlon enabling the underreamer to pass throu h the casing,

thereby not only permitting t e tool to be again lowered in the casing without adjust- Teaming.

ment but relieving the mechanism of the violent stress to which it would be subjected as a resultv ofthe unrestricted expansion of the cutting means to drilling position when the underreamer passes out ofthe top of the casing; and also enabling anew blt to be substituted with a minimumfexpenditure of labor.

Another ob'ect of the invention is to provide mean'sor actuating an underreamer bit so' as to cause the `portions thereof.nor' mally. projectingbeyond the ripher' of the stock to be withdrawn wi 'n the ines ofthe stock, thus enabling the tool to pass through the casing of the well; and a furtherl object of the invention is to produce an funderreamer having a bit formed with a cutting portion on its, lower side'in alinement rtions adapted to perform the function o under- The primary feature ofthe invention, generally stated, consists in constructing the underreamer with a stock and with cutting means movablyr mounted thereon, said cutliugmeansbelng-adapted when in position to pro]ect outwardly beyond the periphery of said stock and also being adapt'- Aed toassume an inoperative position pera strong, reliable and efficient tool employ-v mitting the underreamer to pass through the casing of a well, and in movably mounting on said stock automatically operating means for retaining said cutting means in inoperative position upon the withdrawal of the underreamer from the well casing, said last named means being adapted upon lowering the underreamer into the casing to be brought to a position permitting said cutting means to assume the ldrilling position upon the issuance of the underreamer through the bottom ofthe casing.

Another feature of the invention consists in providing the underreamer with a stock, a spring, cutting means having cuttingportions adapted when in drilling position to project outwardly be ondthe periphery of said stock and also a apted to assume an moperative position permitting the tool to pass through the casing of a well, and with means operatively connecting said cuttin means to said stock through said spring, and in pro-v viding means for relieving said cutting means of the pressure of said spring during the movement of said cuttingv means to an inoperative position allowin the underreamer to pass through the we casing.

Still another feature of the invention oonsists informing the bit of an underreamer with a cutting portion on its Vlower side and with a bearing face on its upper side to enbeing shown' in drilling position an lower portion of the well casing through which the device operates .being shown Figure 2- is a detail vertical sectional view` of the underreamer Yshown'in Fig. 1, the cutting means beingiu the inogative 'tion enabling the tool topass t ugh e well casing, portions-of the device being brokenr 1 is an elevation `of an under` reamer embodying the inventiomthe laway and the upper end` of the well being indicated by dotted lines.

Figure 3 is a det-ail vertical sectional view similar `to Fig. 2, but illustrating vthe positions assumed by the parts in drilling.

Figure 4 is adetail elevationiof the underlreamer showing the parts in drilling position, the upper portion of the device being broken away and the view being taken at right angles to that shown in Fig. 1.

Figure 5' is a detail longitudinal section of a portion of the stock of the und'erreamer. Figure 6 is a section on the line 6 6,

Fig. 3.

igure 7 is a section on the line 7-7, Fig. 3.v

Figure 8 is a section on the line 8--8, Fig. 3.

Figure 9 is a detail vertical section of the lower end of theunderreamer, theparts being in drilling position."

Figure 10 is a detail sectional view of the lower end of a modified form of undervthe parts when the tool is withdrawn from the well casing.

Figure `14 is a sectional view on the line n n, Fig. 12.

Figure 15 is a sectional view on the line The stoc 1 of the underreamerA is preferably provided at its upper end with a threaded tapered pin 2 forming means for connecting the lunderreamer to the devices with which it is associated inA drilling. Below vthe tapered pin the stock mayconveniently be provided with the usual wrench seats: 3. The stock isformed with a downwardly opening longitudinally extending chamber or recess 4 adapted to receive -a spring 5 andcooperating rod 6 through which the bit 7 is yieldingly connected to the stock; The lower end o the trod 6 is movably connectedto the central portion of the cutting means 7, preferably by forming said rod with an eye for recei' a pivot pin 8 which extends into suitable pivoteopenlngs 9',with which the cuttingmeans or bit' is provided. .At its upper end the said rod may be threaded to receive a nut 10 which holds in place a washer 11 bearing upon the u per end ofl the Yspring 5. Intermediateo its length the is slotted to receivea transversely extendin key 12 whose ends project-into longitudmallyI extending' slots 13 o through opposite sides of the stock 1 an communicatl with the chamber4v within which the ro 6 o erates. 'Where the turning movement of t e bit 7 is eected without any accompanying lateral movement of the rod with respect to the stock, said rod may be enlarged adjacent the key 12, as indicated at 14, thus not only reinforcing the rod adjacent the slot therein, but also preventing inv trusion of mud. Above the enlargement 14 the lrod-6 passes through a collar 15 which may be secured within the recess 4 of the stock by means of pins 16 to constitute a cesses 19 formed in the slides and the ends of said key being preferabl of somewhat reduced dimensions to aior shoulders limiting the inward movement of the slides. For the purpose of introducin .the pins 18 in the assembling of the mec anism the stock is preferably provided atits periphery somewhat below the position occupied by'said pins during drilling with a pluralityof opposit'ely disposed depressions 20, permitting the pins 18 to be put in place when the key 12 and slide 17 are drawn downwardly a short distance.

If desired, the recesses of the Vstock in which the slides 17 operate kmay be somewhat wider at the periphery of said stock than inwardly thereof and may conveniently be formed with outwardly. flaring side walls 21 forming beveled guides. against which the correspondingly beveled sides of the slides 17 bear. The slide 'receiving recesses verse slots 13 of the stockare made suiciently' deep to receive the thickened portions 23 with whichthe slides 17 are referably formed adjacent the ends o the transverse key 12, and also to,

adV

*lilo i rtions 22 of the jacent the transpermit the blocks 24 mounted on said slides to beforced I inwardly toward the center of the stock by the well casing. B the 1 ent of the portions 23 of the s 'des' wit-h e stop Shoulders 25 of thestock the downward or spr' compressing movement oftherod'is Y to an amount ensuring at all times'thefpropp er operative relation of the by which the turning or rotation of the .bit 7 withl respect to-said rod and the underreamer stock iseiected. Y vThe slides 17 are furnishedgwith l or projections adapted to'extend outwa y b e- 1w.

youd the periphery of the stock 1 so as to e capable of contacting the lower end of the well casing 26 and are also adapted to move inwardly toward the. axis of said stock so as to pass through the casing. Instead of rigidly connecting.` these lugs or projections to the 'slides 17 which would necessitate an` inward movement of the slides to permit the underreamer to pass through the casing,v said projections are preferably formed as blocks 24 which are movably mounted on the rrespective Slides with capability of moving inan-d out transversely of the stock 1. The outer faces 27 of lthe blocks may be rounded to conform to the curvature of the exterior of thev stock 1, and the outer portions of their upper ends are preferably beveled or inclined as at 28 for the purpose of causing said blocks to be forced inwardly toward the axis of the stock when the blocks are forced against the ends' of the wellcasing in the operation of withdrawing the underreamer from the well. In order that the blocks 24 may be reversible their lower sides may be similarly provided with beveled faces 28. To limit their outward radial movement the blocks 24 are preferably `provided with oppositely disposed longitudinally extending flanges 29 which are overlapped by corresponding portions 30 ofthe respective slides 17 and to compel the expansion of said blocks when they have passed out of the lower end of the casing 26 the stock 1 is formed with inclined or beveled shoulders 31 with which Vthe upper ends of the blocks are respectively adapted to engage. lVhen by reason of the expansion of the spring are caused to move upwardly on the stock 1, the blocks 24 will cooperate with the inclines 31 and thereby be forced outwardly to their full extent.

The underreamer is providedl with means movably mounted on' the stock 1 for retaining the cutting means or bit 7 ina position permitting the underreamer to pass through the well casing, the said retaining means being automatically operable to maintain the cutting means in said position 4upon the withdrawal of the tool from the well. The

- retaining means preferably employed consist of a plurality of oppositely disposed spring pressed` latchesy 32 pivotally mounted upon the stock 1 by means of pins 33. The latches operate in recesses' 34 of the stock which extend above and communicate with the recesses for the slides 17 the said recesses 34 being of a depth sufficient to enable said latches to assume a position permitting them to pass through the casing 26. Springs 35, which are operatively interposed between the respective latches and the stock 1 and which are preferably of leall form, constantly tend to move said latches outwardly beyond the periphery of the 5 the slides 17 stock, as illustrated in Fig. 2. When thus expanded the latches 32 will engage the upper end of the casing 26 when the underreamer is lowered into the well, such engagement of the latches with the casing resulting. during the lowering of the underrealner, in forcing the said latches inwardly against the pressure of the leaf springs 35 until the latches are enabled to enter the casing. To effect this inward camming of the latches in an efficient manner each of them may advantageously be lformed on its outer. side with a. sloping or beveled shoulder 36 for cont-acting with the upper end of the well casing.

The portions 37 of the latches extending Abelow the sloping shoulders 36 are of reduced cross section so that they may freely enter the well casing 26 before the latches 32 are moved inwardly when the underreamer is lowered into the well and also in order that said latches may move outwardly and assume-the position shown in Fig. 2 before they pass entirely above the upper end of the casing. Vhen in an expanded position the lower ends of the latches overlie the upper ends vof the respective slides 17 thereby preventing an upward movement of the latter with respect to the stock 1 and thus checking the expansion of the spring .5 which would result in causing the cutting means i orbit 7 to be rotated to its normal or drilling position. To limit the outward movement of the latches when the underreamer iswithdrawn from the Well their lowerl ends may be provided with lugs 38 adapted to overlap the neighboring inner faces of the slides 17. When. as shown inFig. 3. the parts of the underreamer are in drilling position the lower ends 37 of the latches stand behind the upper ends of the slide 17 and the latches thus are prevented from moving outwardly. j

The cutting means 7 which is yieldingly mounted upon the stock 1 through the instrumentality of the rod 6 to which it is movably connected, 'is adapted when in drilling position to project outwardly beyond the periphery of the stock 1 and beyond the well casing, and is also adapted to assume an inoperative position enabling it to pass through the casing. means employed preferably is constructed as an integral bit 7 having oppositely disposed cutting portions 39 adapted, when in drilling position, to project "outwardly bevond the periphery of the stock, and also lll) The cutting having a cutting portion 40 located between is attached to said rod.

cutting portions 39. As shown in Figs. 1, 3 and 4, the ends 42 of thebit 7 may be and preferably are lconically curved, being tapered upwardly toward the lower' end of the stock. The bit is slotted upon its upper the rod 6 and consequently preserves the the spring seat 15 in place.

strength of the bit.

The lower end of the stock 1 conforms in shape tothe upper end of the bit 7, thus affording bearing faces 45, 46, 47, 48, 49 and 50 which, when the bit is in drilling position, respectively form seats or bearmgs for the bearing faces or surfaces 51, 44, 52, 53, 54 and 55 of the bit. Ample bearing area for supporting the bit during drilling operations is thus provided.

In orderv to cause it to rotate when the rod 6 effects a compression of the spring 5, the bit 7 is preferably'formed on oppositesides 4with angular slots or guideways 56 which respectively receive inwardly extending pins or trunnions 57 with which the stock is provided at its lower end.. The slots 56 are preferably open ended so as to provide for the clearance of any material which may find lodgment therein during drilling.

The underreamer may be assembled as `follows: The latches 32 carrying the leaf` springs 35 are secured to the stock 1 by their pivot pins 33. The spring rod 6, spring 5 and the spring supporting plug 15 will then be assembled outside of the stock 1 andv inserted in the 'chamber 4 of the stock.`

The pin 16 will then be inserted to retain When these parts have been put inposition the blocks 24 are assembled with -their'respective slides 17 and one of said slides is secured to the transverse key 12 by the pins 18.` Thefree -end of the key .12 is then passed through the slot in the spring rod 6 and the other slide -17 with the block 24 mounted thereon is slidonto the key. The spring rod 6 is then drawn down a short distance until the depressions 2O in the stock are opposite th'e pin ropenings in the vkey slots 12, and the remaining connecting pins 18 are inserted.

, With the rod 6 drawn downwardly the pihs or trunnions 55 of the stock are entered in the guide slots 54 of the bit and the latter is attached tothe lower end of said rod by the pivot pin 8. 1

ing radially of the stock and the sli Vspring 5 is prevented from expandi draw the rod 6 upwardly and pull the bit 7 The operation of the mechanism hereto# fore described will be as follows: Assuming the parts to be in drilling position2 as shown in Figs. 1, 3 and 4, the act of wlthdrawing the tool from the well will cause the blocks or'slips 24 to engage the casing shoe at the lower end of the well casing 26. The upward movement of the blocks being arrested, while the upward movement of the stock 1 continues, causes a relative downward movement of the said blocks until their u per ends pass below the shoulders 31 of t e stock, whereupon the said blocks 24 will move inwardly toward the axis of lthe stock and in such position will enter the well casing. This relative downward movement of the blocks 24 produces a corresponding downwardv movement of the slide 17, the transverse key 12 and the spring rod 6, thus energizing the spring 5 and also allowing the bit 7 to move downwardly with respect to n ,the stock 1. During this downward movethe .bearing faces at the lower end of the stock.

During the upward movement of the underreamer through the well casing the latter prevents the slips or blocks 24 from expandes 17 are consequentl retained in a position corresponding tot e inoperative position of the bit 7. During this upward movement also the latches 32 are maintained in inward p0- sition by engaging the interior of the well casing 26. As soon, however, as the shoulders 36 of the latches pass above the up er end of the casing 26 (see Fig. 2) these late es expand beyond the periphery of the stock 1 and their lower ends move outwardly and stand over the upper ends of the respectively adjacent slides v17. vIn this position the latches 32 prevent the slides 17 from rising on the stock, and it thus results that the t0 to drilling position. When the underreamer is wholly withdrawn from the well the bit 7 therefore does not return to drilling position but remains in the inoperative posltion in complete readiness for reintroduction into the well caslng. As has already'been point- ,ed out, the retention of the bit in this position is likewise advantageous in that it relieves the mechanism from the reat strain due to the sudden pulling of the it to drilling position and also because it enables a new n bit to be substituted with great facility.

` Upon again lowering the underreamer into ing the lowery ends of said latches from above the slides 17 and thereby releasing said slides. As the slips or blocks 24 have already entered the well casing before the slides 17 are released from the latches 32, and as the well casing prevents said blocks from eX-\. panding, the slides 17 are prevented from moving upwardly with respect to the stock 1 until the said blocks pass below the casing shoe at the lower' end ot' the casin 26. `The spring 5 thus remains compressed uring the downward passage of the tool through the casing and there is no tendency of the bit 7 to reassume drilling position.

As soon as the blocks 24 pass below the 'casing shoe at the bottom of the casing they expand outwardly, thus Aallowing the stock 1 to continue its downward movement while the spring 5, act-ing through the rod 6, transverse key 12 and slides 17, presses the said blocks upwardly against the casing vshoe.`

The relative movement of the stock and the spring rod and slides thus induced causes the bit. to move upwardly with respect to the stock and to assume its drilling position and also results in causing the upper ends ofthe slides 17 to overlap the lower portions 37 of the latches 32, thus retaining said latches in unlocked position (see Fig. 3).

Figs. 10 and 11 illust-rate an application of the invention to the well known form ot' underreamer disclosed in the Double Patent No. 748,054, heretofore mentioned. In this form ot' underreamer a plurality of relatively movable bits 58 constitute the cutting means, the said bits being movably mounted upon a transverse key 59 which is carried by a spring rod 60 adapted to effect compression of a spring 61 that is housed within the stock 62 of the underreamer. `Mounted upon the stock in suitable recesses on op-v posite sides thereof are a plurality of latches 63 pivotally connected to said stock by pivot pins 64. Oper'atively interposed between the underreamer stock and the respective latches are leaf springs 65 which constantly tend to cause said latches to project outwardly beyond the periphery of the stock. When, as shown in Fig. 11, the bits 58 are in the inoperative position permitting the under-' reamer to pass through the casing, the shoulders 66 of the latches, which are preferably beveled, move outwardly beyond the periphery of said stock as soon as the underrcamcr is withdrawn from the lwell far enough to allow said shoulders to emerge from the upper end of the well casing. In this position of the latches their'lo'wer ends 67 stand above and engage the upper ends of the bits 58, th'us preventing the spring 61 from expanding and thereby retaining the bits 58 in their inoperative position in readiness to reenter the well casing. When the bits 58 are in drilling position (see'Fig. 10) their upper ends overlap thelower ends 67 of the latches and prevent the latter from projecting outwardly beyond the periphery of the stock 62.

In the operation of withdrawing the underreamer from the well the shoulders 68 oi the bits engage the lower end ofthe cas-Vv ing shoe, thus arresting the bits while the upward movement of the stock 62 continues.

This results in a. relative' downward move` ment of the bits allowing them to tilt in- As soon as the shoulders 66 ot' the latches 63 emerge from the upper end `of the casing the springs 65 force 'the latches outwardly and bring their lower ends into locking relation with the bits, thus retaining the-latter in collapsed or inoperative position. lVhen the underreamer is again lowered into the well the shoulders 66 of the latches cncounter the upper end of the casing and the latches are forced inward so that their lower ends 67 are displaced from above the upper ends of the bits. As soon, therefore. as the bits emerge from the lower end of the casing the spring 61 is enabled to expand and thus draw said bits to drilling position.

In Figs. 12, 13, 14 and 15 my invention is shown as .embodied in an underreamer of the character'disclosed in the Wilson vwardly so as to pass through the casing.

Patent No. 827,595, already mentioned. In

springs 74 so as to project beyond the periphery of the stock.v On account of the small amount of space available for the latches in this form of underreamer it is preferred not to locate them in diametrical alinement but to dispose them in an offset relation as shown in Figs. 14 and 15. The form, function and mode of operation of the latches 73 are as heretofore described with respect to the latches 63.

I claim 1. An underreamer having a stock, cutting vmeans movably mounted on said stock and adapted `when in drilling position to project outwardly beyond the periphery of said stock and also adapted to assume aninoperative position enabling said under-` 'reamer'to pass through the casing of a well,

and means movably mounted on said stock 2. An underreamer havin a stock,v cutting means movably mounte on said stock,

said cutting means being adapted when in drillin position to pro ect outwardl beyond t e periphery of t e stock and eing also adapted to assume an inoperative position permitting the underreamer topass through the casing of a we1l,'and means moyabl mounted on said stock operating upon t e withdrawal of the underrcamer from said casing to retain said cutting means in inoperative position, said last named means being adapted'upon the entry of the underreamer in the casing to be actuated to thereby ermit said cutting means to assume a drilling position upon the issuance of the underreamer through the bottom of said casing. ,j

3. An underreamer havin a stock, cutting means movably mounte on said stock, said cutting means being adapted when in 'drilling .position to project outwardly beyond the periphery of said stock and being also adapted to assume an inoperativeposition permitting the underreamer to pass through the casing of a welland means mounted upon said stock adapted upon moving outwardly from the periphery of said stock to maintain said cutting means in inoperative position.

4. An underreamer having a stock, a

spring, cutting means yieldin ly connected to said stock through said" spring, said cutting means being adapted when in drilling position to project outwardly beyond the periphery of said stock and also being adapted to assume an inoperative position permitting the underreamer to pass through the casing of a well, saidspring being energized when said cutting means is in inoperative position, and means mounted upon vsaid stock operatin upon the withdrawal of the underreamer rom the casing for retaining said spring in energized condition.

5. An underieamer havin a stock, cuttin means movably mounte on said stock, sai cutting means when in drillin position being adapted to project outwar( ly beypnd the periphery o said stock and also ing adapted to assume an inoperative position permitting the underreamer to pass through thecasing of a well, means movably mounted on said stock and adapted to move outwardly beyond the periphery thereof for maintaining said cutting means in inoperative position, and means for preventing said -last named means from executing an out ward movement with respect to said stock when the underreamer issues lthrough the bottom of the casing.

6. An underreamerhaving a stock, cutting means movably mounted on said stock, said cutting means being adapted when in drilling position to pro'ect outwardly beyond the periphery of sai stock and also being adapted to' assume an inoperative position permitting the underreamer to pass through the casing of a well, and spring actuated means for maintaining said cutting means in inoperative position, said s ring actuated means having a constant ten ency to assume a position for retaining said cutting means vin inoperative position vand -automatically operatingupon emergence lfrom the 'top of the casing of a well to retain said cutting means in ino erative position. i

7, An un erreamer having a stock, a spring, cutting means Vyieldingly connected to said stock through said spring, said cut-- ting means being adapted when in drilling position to project outwardly beyond the`pe-" riphery of said stock and also being adapted to assume an inoperativeposition permitting the underreamer to pass through the casinor of a well, a spring actuated latch mounted on said stock and adapted to move` outwardly beyond the periphery thereof, said latch eing adapted upon moving outwardly to retain said cutting means in inoperative position,- and means movable by said s ring for preventing outward movement o l said latch-upon the issuance of the underreamer through the bottom of the casing.

8: An underreamer having a stock, a spring, cutting Vmeans yieldingly connected to said stock through said spring, said 'cutting meansbeing adapted when in drilling `position to project outwardly beyond the periphery 'of the stock and also Vbeing adapted to assume an inoperative position permitting the underrea'mer to pass throu h the casing l of a well, a plurality of latc es pvotally mounted upon said stock, and springs operatively interposed between said stock and said latches and constantly tending to move said latches outwardl the underreamer to pass through ,the'casing of al well, said spring being adapted to be energized by the movement of said cutting means to ino rative position and being adapted to in uce the return of said cut` ting means to drilliigaposition, a plurality ofoppositely4 disp latches pivotally mountednpon said stock, said latches being adapted upon an outward movement beyond the peripheyof said to assume a posibeyond the periph- .ery of said stock, sai latches when moved tion preventing said sprin lfrom returning 10. An underreamer having a stock, a-

spring, a rigid bit yieldingly connected'to said stock through said spring, said bit having cutting portionswhich when the bit is in drilling position project outwardly beyond the stock on opposite sides thereof, and means for causing said bit to assume a position permitting the underreamer to pass through the casing of a Well, said means being operatively associated with said stock and bit members and including a pin and a 'slot having angularly disposed portions for receiving said pin, said pin being carried by one of said members and said slot being formed in the other of said members.

11. An underreamer involving a stock and cutting means, together with spring means for normally holding said cutting means in Vcutting position, said cutting means having integrally connected cutting portions adapted when in drilling position to project outwardly beyond the periphery of the stock on opposite sides thereof and also adapted to assume an inoperative position permitting the unde-rreamer to pass through the casing of aI well, said means also including a straight transversely disposed cutting portion lying within the periphery of said stockl when the said cutting means is ir. drilling position.` i

12. An underreamer involving va stock and cutting means, together with means for moving said cutting means to cutting position, said cutting means having integrally united cutting portions adapted when in drilling position to project outwardly beyond the periphery of said stock and also adapted to assume an inoperative position permitting the underreamer to pass through the casing ofa well, and said cutting means also having a cutting portion extending radially of said stock between the cutting portions aforesaid within the periphery of said stock.l

13. An underreamer involving a stock, a bit movably connected to said-stock, and means for moving said bit to drilling position, said bit having cuttingportions adapted when the bit is in drilling position to project outwardly beyond the periphery of said stock on opposite sides thereof and also adapted to assume an inoperative position permitting the underreamer to pass through the casing of a well, said bit also having a cutting portion integrally united to the cutdially of said stock when said bit is in drilling position.

14. An underreamer involving a stock, a bit movably connected to said stock., and yielding means for moving said bit vto drilling position, said bit having cutting portions adapted when the bit is in drilling position to project outwardly beyond the periphery of said stock on opposite sides thereof and also adapted to assume an inoperative posi- `tion to' permit thek underreamer to pass through the casing of a well, and said bit also having a plurality of straight cutting edges sloping upwardly from the central portion of said bit toward the said cutting portions.

15. An underreamer bit having curved cutting portions at its opposite ends, a straight cutting portion intermediate of and extending at an angle to said curved outting portions and a bearing facel upon its upper. side, said portions first named being adapted to project outwardly beyond the periphery of the stock of an underreamer, and said bearing face being adapted to engage an underreamer stock.

16. An underreamer bit formed with an angular slot adapted to receive a member carried by an underreamer stock and having a centrally disposed cutting portion on its lower side and a bearing face on its upper side, the ends of said cutting portion being adaptedto project outwardly beyond the stockof an underreamer, and said bearing face being adapted to engage an underreamer stock.

17. An underreamer 'having a stock, a spring, a rigid bit, and a rod movably connected to said bit and adapted to energize said spring, said bit-being formed with an angular slot and having cutting portions adapted when in drilling position to project outward ly beyond the periphery of said stock and also being adapted to assume an inoperative position permitting the underreamer to pass through the casing of a well, and said stock being provided with a pin extending into said slot. l

18. An underreamer having a stock provided at its lower end with bearing faces for` resisting the upward thrust of a bit, a spring housed within said stock, a bitv having bearing faces adapted to engage the said bearing faces of the stock, said bit having cutting portions which are adaptedwhen in drilling position to projectoutwardly beyond the periphery of said stock and which are also adapted to assume an inoperative position permitting the underreamer to pass through spring, and means for rotating said bit while out of contact Awith said bearing faces Vof the stock to cause said bit to assume a poting portions aforesaid and extendlng raspring, a bit havin-g cutting portions adapted when in drilling position to project outwardly beyond the periphery o said stock and also adapted to assume an inoperative position permitting the underreamer to pass through the casing of a well, a rofl pivotally connected to said bit and adapted to energize said spring when said bitis caused to assume the position for passing through the well casing, and means for causing said bit to rotate upon said rod, said rod being capable of longitudlnal movement only wlth respect to said stock. t

20. An underreamer having a stock, a spring, a bit having cutting portions adapted when in drilling position to project outwardly beyond t-he periphery'of said stock and also adapted to assume an-inoperative position permitting theunderreamer to pass through the casing of a well, a rod to which said bit is rotatably connected and which is adapted to energize said spring when'said bit is caused to assume the position for passinfr through the well casing, and means for re ieving said bit of the pressure of said spring during the rotation of said bit to its` moperative position.

21. An underreamer having astock, a spring, integral cutting means yieldingly connectedlto said lstock through said sprmg 'and having integral cutting portions adapt#tk ed when in drilling position-to project outwardly beyond the periphery -of said stock yand also adapted vto assume an inoperative position permitting the underreamer to pass through the casing of a well, means operatively interposed between said spring and said cutting means for normally maintaining said cutting means in drilling position, an

means for relieving said cutting means of -the pressure of said spring during the movesaid bit to said spring, and a *tend outwardly beyond the periphery of said ment of said cutting position.

22. An'lunderreamer having a stock, a bit having cutting yportions adapted when in drilling position to project outwardly beyond theperiphery of said stock and also adapted to assume an inoperative position permitting means to inoperative the underreamer to Vpass through the casing of a well, means for operative y connectin lurality o .means slidably mounted on said) 'adapted'to actuate said connecting means to :effect a compression of lsaid spring, said last named means having-portions adapted to' exstock and and also adapted to assume an inoperative position permitting the underreamer to pass through the casing of a well, a rod pivotally connectedl to said bit and adapted to ener gize said spring, a key movableV with said rod and having its ends extending into slots formed in said stock, and a plurality of Slides which engage and are adapted to actuate said key to cause said rod to energize said spring, said slides having members movably mounted thereon adapted to pro'ect out-- 'wardly beyond the periphery of sai stock so as to extend beyond the interior of the. said well casing. J

24. An underreamer having a stock, a spring, a bit having cutting portions adapted when in drilling position to project outwardly beyond the periphery of said stock `and also adapted to assume an inoperative position permitting the underreamer topassA through the casing of a well, a rod movably connected to said bit and adapted to energize said spring, means slidably mounted on said stock for actuating said rod to energize said spring, and means movably mounted on said stock forl retaining said last named means in the position in which said spring is energized.

25. An underreamer having a stock formed with a spring receiving chamber, a

:spring within said chamber, a seat for said spring securedto said stock, a slotted rod eXtehdinglt-lirough and adapted to compress said spring, a bit pivotally connected to the lower end of saidjrod, said bit having cutting portions adapted when in drilling -position to project outwardly beyond the periphery'of said stock and also adapted to assume an inoperative position permitting the underreamer tol pass through the casing of a well, a key extending through the slot in said rod, slides connected to the opposite ends of said key and slidable lon 'tudinally with respect to said stock, and a p urality of blocks movably mounted' on the respective slides, said blocks being adapted to assume a position permitting the underreamer to ass throu h the casing-of the well and being also a apted to project outwardly from the periphery of .said stock beyond the interior diameter ofthe well casing.

`26. An' underreamer having a stock formed with an interior chamber extendin longitudinally thereof, a spring within sa' chamber, a rod extending through and adapted to compress said spring, a bit pivvotally connected to said rod, said bit having cutting portions' adapted when in drilling position toproject outwardl1 beyond the periphery of said stock and a so adapted to assume an inoperative position permitting the underrea-mer to rpass through the casin of a well, and means adapted to be actuate by the said well casing for causin said bit. to assume a position permitting eunderto assume a position permitting t reamer to pass through the well casing, said rod being formed with an enlar ed portion which cooperates with the wa ls of said chamber to guide saids rod.

27. An underreamer having a stock, a spring, a bit having cutting portions adapted when in drilling position to roject outwardl beyond the periphery o said stock and a so adapted to assume an inoperative position permitting the underreamer to pass through the casing of a well, a rod pivotally connected tov said bit and adapted to compress said` spring, a lurality of slides mounted upon said stoc and movable longitudinally thereof, means for operatively connectin said slides to said rod, a pluralityy of Lllocks movably mounted upon the respective slides, said -blocks beingx adapted e underreamer to pass through the casing of a well and being adapted to project from the periphery of said stock beyond the interior diameteror` the well casing and also being adapted to be actuated by said well casing to operate said slides, and a plurality of spring-pressed latches mounted upon said stock and respectively adapted to engage said slides to lock the latter in a position corresponding to the inoperative position of said blt.

28.`An underreamer having i a stock, a sprin a bit having cutting portions adapted w en in drilling position to project outwardl beyond the peripheryof said stock and a so adapted to assume an inoperative position to permit the underreamer to pass 'through the casing of a well, a rod pivotslides to retain thelatter in a. positlon cor.

responding to the inoperative position of said bit,I said latches being adapted to project outwardly beyond the periphery of said stock when the underreamer 1s withdrawn from the well casing, and said slides constituting means for retaining said latches in a retracted posit-ion corresponding to the drilling position of said'bit.

29. A welll drilling tool involving a bit having curved segmental cutting portions at its opposite ends and a rectilinear cutting portion intermediate of and extending radially with respect to said segmental cut-A tinlg port-ions.

testimony whereof I ailix` m'y signature. A

ALFRED G. 'HEGGEM

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