US2734768A - warner - Google Patents

Description

Feb. 14, W D WARNER HYDRAULIC OVERSHOT 2 Sheets-Sheet l FIG. 2

FIG. 3

Filed March 19, 1952 INVENToR. W. D. WARNER ATTORNEY Feb. 14, 1956 w. D. WARNER HYDRAULIC ovERsHoT 2 Sheets-Sheet 2 Filed March 19, 1952 ATTORNEY United States Patent() HYDRAULIC OVERSHOT William D. Warner, Oklahoma City, Okla.

Application March 19, 1952,l Serial No. 277,380

9 Claims. (Cl. 294-86) This invention relates to improvements in overshots for removing stuck drill pipe from well bores and more particularly, but not by way of limitation, to an improved overshot adapted to be interposed in a string of wash pipe.-

' As it is well known, during the drilling of deep wells, the drillingbit is frequently forced in a direction varying from the vertical by slanting formations and the like, resultingin a crooked well bore. After the drilling bit has been forced from a vertical course and then returns to a vertical course, the drill pipe positioned above the drill bit frequently wears a small opening adjacent the well bore proper. As a result, when the drill bit is subsequently removed from the well bore, the drill collars, positioned adjacent the drill bit and being of larger diameter and stiller than the drill pipe, are frequently lodged in the narrow opening adajcent the well bore to prohibit cornplete removal of the drill bit. In such a situation, it is then necessary tol cut the drill pipe a distance4 above the drill bit and drill collars. A string of pipe usually called the wash pipe, and being of larger diameter than the drill pipe, is then run into the well bore and telescoped over the upper end of the several drill pipe. Fluid is then forced down through the wash pipe to wash loose the drill pipe and drill collars to facilitate the removal thereof. As the drill pipe is washed loose, it usually falls baci; down to theA bottom of the well bore.

kAt the present time, the usual procedure is to remove the wash pipe from thewell bore and run another string of pipe or tubing into the Well borewith an overshot on the lower end thereof' for removing the fallen drill pipe and drill bit. It will be apparent that the removal of the washy pipe and the insertion of another string of pipe into the well bore entails considerable manhours and lengthens the time during which the well is being drilled.

The present invention contemplates a novel overshot adapted to be interposed in the wash pipe and telescoped down over the stuck drill pipe during the washing operation. As the drill pipe is'washed loose and starts to fall tothe bottom of the Well bore, the overshot engages one of the tool joints remaining on the drill pipe to stop the fall ofy the drill pipe and permit immediate removalthereof. The overshot contains a movable carrier therein which is adapted to move a short distance in the overshot proper during the initial fall of the drill pipe. The carrier is so constructed and arranged with respect to the overshot housing or bowl to provide a shock absorbing action for the carrier and the drill pipe. In this manner the shock resulting from stopping the fall of the drill pipe is reducedv to a minimumand reduces the wear and tear on the wash pipe. It is contemplated to provide two types of overshots; one for engagingtool joints having ilat ends and one for engaging tool joints having tapered ends.

An important objectof this invention is to provide a novel overshot` adapted to be` interposed in a string of washpipe.

Anotherz objecty of,A this invention is tov reduce to a minimum the number of trips or runs of pipe into a well bore for the removal of stuck drill pipe.

A further object of this invention is to catch drill pipe during its fall subsequent to the washing loose of the drill pipe.

Another object of this invention is to provide an overshot wherein the shock of stoppin-g falling drill pipe is reduced to a minimum.

A still further object of this invention is to provide an overshot having a movable carrier therein utilizing a hydraulic shock absorber to control the movement of the carrier.

Another object of this invention is to provide an overshot which may be readily disengaged. from a drill pipe in the event the drill pipe cannot be removedfrom a well bore.

A further object of this invention is to provide anovershot having along service life and which may be economically manufactured.

Other objects and advantages of the invention will be evident from the following detailed description, read in conjunction with the accompanying drawings, which illus.- trate my invention. l

In the drawings:

Figure l is a vertical sectional view, partially in elcvation, of a novel overshot interposed in a string; of wash pipe with a string of drill pipe shown in dotted linesex-V tending through the overshot in a nonfengaging relationship therewith..

Figure 2 isy ay detailed. crossl sectional View of they dogs utilized in the overshot to engage the drill. pipe.

Figure 3 is an exploded View illustrating the assembly of the dogs.

Figure 4 is a vertical crossy sectional view of the overshot shown in Fig. l showing the overshot engaged with a tool joint. v

Figure 5 is a vertical sectional view of a modied over,- shot for engaging tool joints having tapered ends.

Figure 6 is a perspective View of the. upper sectionv of the carrier utilizedA in. the overshot shown inFig. 5..

Figure 7 is a detailed View of. a. frictionshoe utilizedin the modified overshot shown in Fig. 5.

Figure 8 is a detailed cross sectionalview of slips utilized in the overshot shown-in Fig. 5. y

Referring to the drawings in detail, and particularly Figs. 11 andl 4, reference character 2` generally designates a novel overshot, for engaging tool. joints havingiiat ends and interposed in a string of wash pipe 4;, The'overshot 2 comprises a cylindrical, housing 6 constructedinv two sections 8 and l0.; The upper end 12. of the upperhousing sectionv 8 is threadedly connected to one section of the wash. pipe 4, and the lower end 14'of. the 'lowerhousing section 1i) is threadedly connected through the` medie um of a coupling 16 to another sectionof'the washzp'ipe 4. Therefore, the` overshot 2l is'simply interposeduin, kthe wash pipe 4 in axial alignmenty therewith. The sections-8 and lll' of theV housing 6. are threadedly interconnected at 18 (more clearly shown in Fig. 4) in such afmanner-tnat the upper end 20 of the section l0 extends upwardly Into the section 8.

A bore 22,-comparable in diameterv to the inner diametery of the wash pipe 4, extends longitudinally partially through the lower housing section 1l); The bore 22 is enlarged in the central portion of theY sectionA 10to provide a circumferential' tapered shoulder 24. The housing 1'0.-is provided with an upper enlarged section 26 incommunication with the bore 224 and extendingupwardly to one ofthe the upper end 20 of the section 10." A bore 28, al'so f comparable in diameter tothe'l inner diameter of the wash pipe 4, extends longitudinally'partially' through tlieupper housingsection 8; The bore.2i8 is enlarged ati 30'topro.- videa circumferential: tapered' shoulder slightly above the central portion of the upper section 8. The housing 8 is provided with a lower enlarged portion 32 in communication with the bore 28 and is greater in diameter than the enlarged bore 26 of the lower section 10 and is of a size to receive the upper end of the lower housing section 10.

A tubular shaped carrier 34 is reciprocally disposed in the bore 26 of the lower housing section 10. The carrier 34 is of a size to provide a sliding t thereof in the bore 26 and is of a length to extend upwardly into the bore 32 of the upper housing section 8. A circumferential flange 36 is provided on the upper end of the carrier 34 and is of a size to provide a sliding fit thereof in the bore 32. The ilange 36 obviously reciprocates in the bore 32 upon vertical movement of the carrier 34 in the bore 26. The annular space or chamber 38 provided between the carrier 34 and the walls of the bore 32, when the carrier 34 is in an upper position as shown in Fig. l, is normally lled with a hydraulic fluid and preferably a heavy lubricant for purposes as will hereinafter appear.

A plurality of breakable studs 40 (only one of which is shown) are threadedly secured in the upper section 8 of the housing 6 and extend inwardly into the bore 32. The studs 40 are normally disposed below the flange 36 to retain the carrier 34 in its uppermost position as shown in Fig. 1. However, the studs 40 may be broken when a force is imposed upon the upper end of the carrier 34 to permit downward movement of the carrier as will be more fully hereinafter set forth. A pair of diametrically opposed keys or lips 42 extend downwardly from the flange 36 and are adapted to enter complementary grooves or slots 44 provided in the upper end 20 of the lower housing section 10 when the carrier 34 has been moved to a down position as illustrated in Fig. 4.

A plurality of circumferentially spaced T-shaped grooves 46 (see Fig. 3) are provided in the upper outer surface of the carrier ilange 36 to receive and support dog members 48. Oppositely extending studs 50 are provided on the lower end of each of the dogs 48 and are adapted to be rotatably disposed in the outer ends 52 of the respective T-shaped slot 46. The dogs 48 thus may be pivoted with respect to the carrier flange 36 as will hereinafter appear. A pair of spaced apertures 54 are provided in the flange 36 at the lower end of each T-shaped slot 46 to receive small helical springs 56. The springs 56 extend upwardly into the respective slot 46 in contact with the lower end 58 of the respective dog 48. The lower end 58 of each dog 48 is tapered upwardly and inwardly with respect to the carrier ange 36. Thus the force exerted by the helical springs 56 on the tapered ends 58 will yieldably retain the dogs 48 in an inclined position as illustrated in Fig. l. The upper end 60 of each dog 48 is tapered in the same direction (Fig. 2) as the opposite lower end 58 thereof, and is provided with a series of teeth or serrations 62 (Figs. 2 and 3). The teeth 62 are provided to engage the lower end of a tool joint and are disposed at an oblique angle, i. e., the teeth 62 are biased outwardly and upwardly (when viewed from the top thereof with the inner edge of the dog 48 to the left) for purposes as will be hereinafter set forth.

Operation As previously set forth, a string of drill pipe is frequently stuck in a well bore some distance above the bottom of the bore. To remove the drill pipe, the overshot 2 is assembled in a string of wash pipe 4 as illustrated in Fig. l. The carrier 34 is retained in its upper position as shown in Fig. l by the stud 40, and heavy lubricant is provided in the chamber 38 as heretofore set forth. The wash pipe 4 is then lowered into the well bore (not shown) and telescoped downwardly over the drill pipe 64 (shown in dotted lines in Fig. l and solid lines in Fig. 4). The wash pipe 4 is moved downwardly until a tool joint 66 is in the upper portion of the overshot 2 as shown in Fig. l, or a distance above the overshot 2 (not shown). It will be apparent that the inner diameter of the carrier 34, as well as the remainder of the overshot 2, is suiicient to permit substantially free movement of the overshot downwardly over the tool joint 66. Furthermore, the dogs 48 will pivot outwardly against the action of the springs 56 when contacted by the tool joint 66 to permit downward movement of the overshot 2 over the tool joint.

When the overshot 2 is disposed over the drill pipe 64 as shown in Fig. l, fluid is circulated from the surface through the wash pipe 4 and overshot 2 to wash the stuck drill pipe 64 loose. As the drill pipe 64 is washed loose and falls, the lower flat end of the tool joint 66 will engage the teeth 62 at the upper ends 60 of the dogs 48 as shown in Fig. 4. The weight of the drill pipe 64 is then imposed through the medium of the tool joint 66 and dogs 48 to the movable carrier 34. This excessive weight will move the carrier 34 downwardly in the bores 32 and 26 and fracture the retaining stud 40. Vertically spaced apertures 68 are preferably provided in the walls of the carrier 34 to provide restricted outlets for the lubricant from the chamber 38. It will be apparent that as the carrier 34 moves downwardly, the apertures 68 are successively cut off by the upper end 20 of the lower housing section l0 to reduce the outlet area for the lubricant from the chamber 38. The reduction in the outlet area for the lubricant provides an increasing uid pressure force on the lower surface of the ange 36, thereby providing a dash pot action for the carrier 34 to gradually bring the carrier 34 and the drill pipe 64 to a stop. The exhorbitant stresses which would result from the sudden stopping of the falling drill pipe 64 are thus avoided and the shock imposed on the overshot 2 and wash-over pipe 4 is reduced to a minimum. It will be noted that when the carrier 34 is moved to its down position, as illustrated in Fig. 4, the keys 42 are disposed in the complementary grooves 44.

The wash pipe 4 is then raised to raise the drill pipe 64 and remove it from the well bore. In the event the drill pipe v64 again becomes stuck during upward movement of the wash pipe 4, and cannot be removed from the well bore, the wash pipe 4 is lowered to reduce the force imposed by the dogs 48 on the tool joint 66. The wash pipe 4 is then rotated clockwise to release the dogs 48 from the tool joint 66. Since the teeth 62 are biased as heretofore set forth, the teeth 62 will react with the lower end of the tool joint 66 to pivot the dogs 48 outwardly out from under the tool joint 66. The wash pipe 4 and overshot 2 is maintained in continuous rotation and raised through the well bore. lt will be noted that the cooperating grooves 44 and keys 42 will cause rotation of the carrier 34 simultaneously with the overshot 2.

In the event the drill pipe 64 becomes stuck again as set forth above, but before the studs 40 are broken or sheared, the wash pipe 4 may be raised to bring the dogs 48 into contact with the tool joint 66. The lower surface of the ilange 36 will thereby be retained in contact with the studs 40. The` wash pipe 4 and overshot 2 may then be rotated clockwise, whereupon the studs 40 will contact the keys 42 to transmit the rotation to the carrier 34 and dogs 48 to release the dogs as set forth above. The overshot 2 may then be removed from the well bore.

M odifed structure Referring to Fig. 5, reference character 70 generally designates a modified overshot for engaging tool joints having tapered ends and also adapted to be interposed in a string of wash pipe (not shown). The overshot 70 comprises a cylindrical housing constructed in upper and lower sections 71 and 72 respectively. The upper end of the lower housing section 72 is secured to the lower end of the upper housing section 71 by threads 73. The upper end (not shown) of the upper section 71 and the lower end (not shown) of the lower section 72 are 5, adapted' to, be intero nneeted rto lthe wash pipe in the same manner as the overshot 2 shown in Figs. 1- and' 4*.

A bore 74 extends longitudinally through the upper housing section 71 to receive and permit passage of the drill pipe 75V therethrough. The bore 74 is enlarged at 76 to provide a bore 77of greater diameter through the lower portion ofthe upper housing section 71. A bore 78 also extends longitudinally through the lower housing section 72'- and-communicates withthe bore 77. The bore 78 is smaller in diametery than the bore 77Ik for purposes as will be hereinafter set forth.

A lower tubular shaped carrier member 79 is disposed in the lower portionof the bore, 7,7y and extends downwardly into the bore 7-8. The main body portion of the lower carrier 79 is of a size to provide a loose sliding fit thereof in the bore 78. A, circumferential flange 80 is provided' on the upper end' of the lower carrier 79 and is of a size to provide asliding fit thereof in the bore 77. The inner periphery of the carrier 79 is tapered downwardly and inwardly atV the upper end 79a thereof. The annular space or chamberl provided between the main body portion of the lower carrier 79vandthe walls of the bore 77, when the carrier 79 is in the upper position as shown in Fig. is normally llediwithrahydraulic uid and preferably aheavylubricant. The lower carrier 79 is retained in its upper position by a pair of diametrically opposed breakable studs 82- threadedly secured in theV side walls ofthe housing section 7lY and extending into the bore 77Y underneath the ange Si). These studs S2 are broken when a large downward force is-imposed on the lower carrier 79 to permitdownwardmovement of the carrier as will be hereinafter setrforth.

Anupper tubular shaped carrier 83 is disposed in the bore 77 above the lower carrier 79 and is of a size to move freelythroug-h the bore77 as will be hereinafter setforth. A pairof diametricallyropposed arcuate slots 84 are provided in the upper end-l 85- of thev carrier 83 as is'clearly shown in Fig. 6. The slots 84'are adapted to receive a pairl of diametrically opposed locking studs 86 extending inwardly into the bore 77 above the carrier 33 tolock the car-rier 83 in an upper-'position (not shown) as will be hereinafter set forth.

A plurality of arcuate springs $7k are secured in complementary slots 8S` in the upperY inner.v portion of the carrier 83` by suitable bolts or the like (notshown). The springs 871 are commonly. called. belly springs and are adapted' toi engage the tool joint 89 uponv movement of thetool joint downwardly through the overshot and'provide movement of the carrier 83A with the tool joint 89. The springs 8.7' may becompressed by the tool joint 89 in the usual manner to permit movement of the tool joint S9 through the carrier SSLwhen the carrier is locked in the overshot 7i) as` will bemore fully hereinafter set forth.

Circumferentially spaced friction shoes 90 are also provided in the carrier S3. below the belly springs 87 to engage the tool joint 89. Each of the friction shoes 90 is disposed in a complementary slot 91 provided in the wall ofthe carrier 83:.as shown in Fig. 7. Lips or flanges 92 extend from the innerwall of the carrier 83 and overlie the opposite ends of each slot 91 to engage the upper and lower ends of the friction shoe 90 and limit the inward movement of the shoe. A closure member 93 is secured to the outer, wall of the carrier 83 by any suitable means (not shown) over eachof the slots. 91 to prevent drilling mud and the like from entering the slots 91 and interferl ing with the operation of the friction shoes 90. A pair of small helical springs. )d` are provided in each slotI 91 and are anchored at their opposite ends to the closure plate 93 and the friction shoe 90. The springs 94 obviously continuously urge thek shoes 90 inwardly into the carrier 8 3 for engagement with the tool joint 89. Furthermore, the shoes 90 maybe moved. outwardly inthe slots 91 upon contact with the tool joint 89 to permit passage offthe tool joint through` the carrier 83, however, the shoes; 90.` will. tend to.drag` on thetoolE joint 89Y and (i tend to move the carrier 83 with the tool joint. The friction shoes 90 and belly springs 87 perform the saine function and may be interchanged at will. That is, either one or both may be used.

A plurality of circumferentially spacedA slips 95 are secured to the lower end 96 of the ycarrier 83 and are adapted to enter the upper tapered end 79a of the lower carrier 79; The slips 95 extend intov complementary T- shaped slots 98 provided in the outer surface of the carrier 83 at the lower end 96 thereof; Studs 99 extend from opposite sides of each slip 95` adjacent the upper end 160 thereof to pivotally support the slips 95 in the T-shaped slots 98. An aperture 101 is provided in the wall of the carrier 83 at the upper end of each of the T-shaped slots 98 to receive a small helical spring 102. The springs 102 extend downwardly and engage the upper end 100 of the complementary slip 95,. The, upper end 100 of each slip 95 is tapered downwardly and outwardly; therefore, the force imposed by the helicaly springs 102 thereon tends to pivot the slips 95 on their supporting studs 99 and retain the slips 95 in an inclined position opposite to the position illustrated in Fig. 5, for purposes as will be hereinafter set forth.

Operation To remove the stuck drill pipe 75 from a well bore (not shown), the overshot is interposed in a string of wash pipe with the carriers 79 and 83 in the position. shown in Fig. 5, and with heavy lubricant disposed in the chamber 81 around the lower carrier 7,9. The over,- shot 70 is then lowered into the well borek and is tele; scoped downwardly over the drill pipe until the tool joint 89 is in the position above the upper carrier 83 as illustrated in Fig. 5. The inner diameter of the lower carrier '79 is of sufficient size to permit free movement of the tool joint 89 therethrough, and the lockingv studs 36 will contact the upper end 85 of the upper carrier 83 to limit the upward movement of the carrier caused byengagement of the friction shoes and belly springs S7 with the tool joint 89. When the carrier 83 isstopped in the housing 7l, the tool joint 89 will compress, the springs 87 and move the friction shoesY 90 outwardly to permit movement of the carrier 83 downwardly over the tool joint with the housing 71.

Fluid is then circulated through the wash pipe and overshot 70 to loosen the drill pipe 75 and cause the drill pipe to fall downwardly in the well bore. As the tool joint 89 moves downwardly through thebore 7,7, it engages the belly springs 87 and friction shoes 90 yto move the upper carrier S3 simultaneously downward. As the slips enter the upper tapered end 79a of the lower carrier 79, they are forced inwardly until their lower ends are moved into contact with each other adjar,

cent the drill pipe 75 as shown in Fig. 5. The upper carrier 83 will then be instantaneously stopped, whereupon the tool joint 89 will move on downward through the carrier 83 until the lower tapered end 103 thereof engages the slips 95. Atithis time, the weight of the falling drill pipe 75 is imposed through the tool joint 89 and slips 95 to the lower carrier 79, thereby forcing both carriers 79 and $3 downwardly simultaneously with the drill pipe 75.

The studs 82 will bel broken during` the initial down-` ward movement of the lower carrier 79-asyheretofore set forth. As the lower carrier 79 is moved downwardl in the bore 77, the heavy lubricant contained inl the annular chamber 81 will be ldischarged through the small annular opening (not shown) provided between the outer surface of they carrier 79 and the wallsv of the lower bore 78. It will be apparent that this outlet for the fluid will be limited to provide a iiuid pressure force on the lower area of the flange 80, thereby decreasing the speed of the downwardly moving drill pipe 75. Furthermore, the further the lower carrier 79 enters the bore 78, the more friction will beprovidedv to restrict the discharge of the lubricant. Thus, the pressure force exerted by the lubricant in chamber 81 on the lower area of the flange 80Vwill be substantially constantly increased to gradually decrease the speed of the drill pipe 75. The carrier 79 is stopped upon contact of the flange 80 with the upper end of the lower housing section 72. In this manner, the drill pipe is gradually brought to rest to provide a minimum strain on the overshot 70 and the interconnected wash pipe. It will be understood that vertically spaced apertures (not shown) may be provided in the walls of the lower carrier 79 to form outlets for the lubricant from the chamber Si in conjunction with, or in the place of, the outlet formed by the annulus between the outer surface of the carrier 79 and the walls of the lower bore 78.

The overshot 70 may then be raised to remove the drill pipe 75 from the well bore. ln the event the drill pipe 75 again becomes stuck, the overshot 70 is lowered to bring the locking studs 86 into contact with the upper end 85 of the upper carrier member 83. During the downward movement of the overshot 70, the belly springs 87 and friction shoes 90 will engage the tool joint 89 to retain the upper carrier 83 in a fixed position and permit movement of the housing section 7l thereover. However, the lower carrier 79 will move downwardly simultaneous with the housing section 7i by virtue of friction between the flange 8i) and the bore 77 as well as gravity to remove the slips 9S from the tapered section 79u. As the studs 86 contact the upper end of the carrier 83, the housing section 7l is continued moved in a downward direction and is simulatneously rotated counterclockwise. However, the springs 87 and shoes 94) contacting the tool joint 89 will restrain rotation of the carrier 83. Thus, the studs S6 are moved into the slots S4 into a position underneath the overhanging lips 165. The overshot 70 may then be raised and removed from the well bore over the drill pipe 75. Since the upper carrier 83 is then in spaced relation to the lower carrier 79, the slips 95 will be sprung outwardly by the action of the helical springs 102 to preclude contact of the slips with the tool joint 39, or other tool joints (not shown) above the tool joint 89, and permit free upward movement of the carrier section 83 with the housing 7l.

From the foregoing, it is apparent that the present invention provides a novel overshot adapted to be interposed in a string of wash pipe whereby the number of trips into a well bore for the removal of stuck drill pipe will be reduced to a minimum. The overshot catches the drill pipe upon its being washed loose in the well bore to preclude the necessity of again lishing for the drill pipe. Each embodiment of the overshot utilizes a movable carrier having means to engage the tool joint. The carrier, in each embodiment, has a circumferential ange providing a downwardly facing pressure area on which is applied an increasing fluid pressure force dur ing downward movement of the carrier to gradually stop the downward movement of the falling drill pipe and reduce the strain on the wash pipe to a minimum. Furthermore, the overshot may be readily disengaged from the drill pipe in the event it cannot be removed from the well bore to permit removal of the overshot and wash pipe.

Changes may be made in the combination and arrangement of parts as heretofore set forth in the specification and shown in the drawings, it being understood that any modification in the precise embodiment of the invention may be made within the scope of the following claims without departing from the spirit of the invention.

I claim:

l. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, coinprising a tubular housing, tubular carrier means reciprocally disposed in the housing, breakable lugs in the housing engaging the carrier means to normally retainjthe carrier means in one position in the housing, an outwardly extending circumferential ange on the carrier means, an inwardly extending circumferential flange on the housing providing a chamber between said flanges for hydraulic fluid, means carried by the carrier means to engage the drill pipe tool joint upon movement of the tool joint downwardly through the housing, and restricted outlet means for said hydraulic fluid to control the downward movement of the carrier.

2. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, comprising a tubular housing, tubular carrier means reciprocally disposed in the housing, stop means in the housing to limit the downward movement of the carrier means, means normally retaining the carrier means in spaced relation to said stop means, means carried by the carrier means to engage the drill pipe tool joint upon movement of the tool joint downwardly through the housing, a downwardly facing pressure area on said carrier means, and means for maintaining a hydraulic uid pressure on said area to control the downward movement of the carrier upon engagement thereof with the tool joint.

3. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, cornprising a housing having a bore extending therethrough, said bore having an upper large diameter portion and a lower small diameter portion, a tubular shaped carrier reciprocally disposed in the small diameter portion of said bore and extending upwardly into the larger diameter portion of said bore, a circumferential flange on the upper end of the carrier of a size to provide a sliding fit thereof in the larger diameter portion of the bore, breakable means in the housing for retaining the carrier in an upper position in the housing, a body of lubricant in the larger diameter portion of the bore under said circumferential liange to resist downward movement of the carrier, restricted outlets for the lubricant, and means on the carrier to engage the drill pipe tool joint upon downward movement of the tool joint through the housing.

4. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, comprising a tubular housing, a tubular carrier reciprocally disposed in the housing, dogs pivotally supported on the carrier, means constantly urging the dogs to a position extending inwardly into the carrier, whereby the dogs will engage the drill pipe tool joint upon movement of the tool joint downwardly through the housing and impose the weight of the tool joint on the carrier, means on the carrier providing a downwardly facing pressure area, and means for maintaining a fluid pressure force on said pressure area to control the downward movement of the carrier and tool joint.

5. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, comprising a tubular housing, a tubular carrier reciprocally disposed in the housing, dogs pivotally supported on the carrier, means constantly urging the dogs to a position extending inwardly into the carrier, whereby the dogs will engage the drill pipe tool joint upon movement of the tool joint downwardly through the housing and impose the weight of the tool joint on the carrier, a circumferential flange on the carrier, a coniining chamber underneath said flange for the reception of uid, and means to control the discharge of fluid from the chamber to control the downward movement of the carrier and tool joint.

6. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, comprising a tubular housing, a tubular carrier reciprocally disposed in the housing, dogs pivotally secured to the upper end of the carrier, spring means in the carrier constantly urging the dogs in a tilted position extending inwardly and upwardly into the carrier, whereby thc dogs will engage the lower end of the drill pipe tool joint upon downward movement of the tool joint through the housing to impose the weight of the drill pipe on the carrier, means providing for hydraulic control of the downward movement of the carrier to gradually stop the downward movement of the drill pipe, and teeth on the upper ends of the dogs, said teeth being formed on a bias whereby upon rotation of the carrier in one direction the teeth react on the tool joint to pivot the dogs outwardly from under the tool joint.

7. An overshot adapted to bev telescoped over a string of drill pipe having a tool joint interposed therein, cornprising a tubular housing, a tubular carrier reciprocally disposed in the housing, dogs pivotally secured to the upper end of the carrier, spring means in the carrier constantly urging the dogs in a tilted position extending inwardly and upwardly into the carrier, whereby the dogs will engage the lower end of the drill pipe tool joint upon downward movement of the tool joint through the housing to impose the weight of the drill pipe on the carrier, means providing for hydraulic control of the downward movement of the carrier to gradually stop the downward movement of the drill pipe, teeth on the upper ends of the dogs, said teeth being formed on a bias whereby upon rotation of the carrier in one direction the teeth react on the tool joint to pivot the dogs outwardly from under the tool joint, keys on the carrier, and complementary slots in the housing to receive the keys when the carrier is in a down position, whereby rotative movement of the housing will be imparted to the carrier.

8. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, comprising a tubular housing, a tubular carrier reciprocally disposed in the housing, dogs pivotally secured to the upper end of the carrier, spring means in the carrier constantly urging the dogs in a tilted position extending inwardly and upwardly into the carrier, whereby the dogs will engage the lower end of the drill pipe tool joint upon downward movement of the tool joint through the housing to impose the weight of the dn'll pipe on the carrier, a downwardly facing pressure area on the carrier providing an annulus between the housing and the carrier, a body of fluid confined in said annulus, means for controlling the discharge of the uid to gradually stop the downward movement of the carrier and drill pipe, teeth on the upper ends of the dogs, said teeth being formed on a bias whereby upon rotation 'of the carrier in one direction the teeth react on the tool joint to pivot the dogs outwardly from under the tool joint, keys on the carrier, and complementary slots in the housing to receive the keys when the carrier is in a down position, whereby rotative movement of the housing will be imparted to the carrier.

9. An overshot adapted to be telescoped over a string of drill pipe having a tool joint interposed therein, comprising a tubular housing, tubular carrier means reciprocally disposed in the housing, a circumferential flange on the outer surface of the carrier means providing an annulus between the housing and carrier means below the flange, hydraulic fluid in the annulus, means carried by the carrier means to engage the drill pipe tool joint upon movement of the tool joint downwardly through the housing, said carrier provided with restricted outlet means for the hydraulic iuid to control the downward movement of the carrier means, and stopfmeans in the housing to limit the downward movement of the carrier.

References Cited in the tile of this patent UNITED STATES PATENTS 1,411,546 Winger Apr. 4, 1922 1,471,775 Brown Oct. 23, 1923 1,494,135 Robinson et al May 13, 1924 2,026,295 Baker Dec. 31, 1935 2,508,285 Otis et al Mayk 16, 1950 2,519,288 Roberson Aug. l5, 1950 2,605,131 Marshall et al July 29, 1952 2,619,374 Davidson Nov. 25, 1952

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