US2618466A

US2618466A - Variable stroke rotary well jar

Info

Publication number: US2618466A
Application number: US21540A
Authority: US
Inventors: Edgar W Bagnell; Wilbur F Bettis
Original assignee: Johnston Testers Inc
Current assignee: Johnston Testers Inc
Priority date: 1948-04-16
Filing date: 1948-04-16
Publication date: 1952-11-18
Anticipated expiration: 1969-11-18

Description

NOV. 18, 1952 E w- BAGNELL ETAL 2,618,466

VARIABLE STROKE ROTARY WELL JAR Filed April 16, 1948 5 Sheets-Sheet l 42W 4 W M M3 ma 69 02 /07 0f 52 WW 177' T115 18min?! 15gg/ /70 /0/ l m6 /700 C 69 705 (2 70 n 97 73 fg] 702 706 f- 70 76 5 l ,70 Bnventor.

EDGAR WJBAQNELL A/D B W/LBUR f.' .BET-ns u y A (lttotneg Nov. 18; 1952' E. W. BAGNELL EVAL VARIABLE STROKE ROTARY WELL JAR Filed April 16, 1948 MM@ f il H loVn -u 5 Sheets-Sheet 2 nvenfo:

EDGAR W BAQNELL AND W/Laun F.' BETT/s Nov 18, 1952 E. w. BAGNELL ETAL VARIABLE STROKE ROTARY wELL.JAR

5 Sheets-Sheet 3 Filed April 16, 1948 Snventors: -DGAR W Bag/VELA. AND 4.3 1/MBAR F EfrT/s Gtorneg Nov. 18, 1952V E. w. BAG'NELL ET AL 2,618,466

VARIABLE STROKE ROTARY WELL JAR Filed April 16, 1948 5 Sheets-Sheet 4 652 y 63 65 6 4 66 5v 65 g d 706 9 70 94 92 96 93 '70 94 99 a@ :i5 15' ,0

L-. A 9a 98, m5 /05 9 L 5 100 70 rfa ma 7 f0.9

97 95 ma U5 4 9/ (Ittorneg Srwentors:

Nov. 18, 1952 E. w. BAGNELL ErAL VARIABLE STROKE ROTARY WELL JAR 5 Sheets-Sheet 5 Filed April 16, 1948 Vmaentors: EDGAR W BHQNELL mw 3 8 7 7 w w A a a M Patented Nov. 18, 1952 VARIABLE STROKE ROTARY WELL JAR Edgar W. Bagnell and Wilbur F. Bettis, Glendale, Calif., assignors, by mesne assignments, to Johnston Testers, Inc., Houston, Tex., a corporation of Delaware Application April 16, 1948, Serial No. 21,540

(Cl. Z55-27) 17 Claims. 1

This invention relates to well drilling equipment, and particularly pertains to a variable blow rotary well jar.

In Well drilling operations it is often necessary to withdraw a section of drill string from a well bore after the section has become accidentally detached from the supporting string either by separation at a point or by a twist-off. The operation of recovering the detached member is commonly known as a iishing operation. In some instances the detached length of drill pipe is lodged in the well in such a manner as to require an enormous amount of force to dislodge it so that it can be withdrawn from the well bore. This operation is performed by a well jar. rIhese jars for the most part have been connected to a fishing tool which engaged the detached part or sh, and which were designed so that when a determined tension strain was imposed on the well jar by a supporting member the jar would release suddenly and its parts would have relative movement to each other, after which a Violent impact is created tending to jar the fish loose from its position in the well bore. This type of jar requires that an intermittent operation must be performed in order to set the jar, tension it, and release it. It is desirable to provide a jar which is continuous in operation and which will set up a succession of jarring blows as the supporting drill string rotates. Heretofore jars of this type have been made but they have created only a relatively small impact blow which was constant, and which could not be varied in magnitude to meet the problem presented. It is the principal object of the present invention, therefore, to provide a rotary well jar including a hammer and anvil, and means whereby a desired tension strain may be set up and suddenly released to impart a jarring blow to the fish, and in which the magnitude of the blowA may be varied adjustably.

The present invention contemplates the provision of a rotary Well jar including upper and lower loosely coupled elements, one carrying a hammer and the other an anvil, and which elements are equipped with rotary clutch mechanism, the parts of which are designed to build up tension strain of a desired magnitude and to suddenly release this force so that it may be expended in impact between the hammer and the anvil.

The invention is illustrated by way of example in the accompanying drawings in which:

Figure l is a view in elevation showing the well jar as associated with a suspending string of pipe and a fishing tool.

Fig. 2 is an enlarged fragmentary section through the upper portion of the well jar as indicated on the line 2 2 of Fig. 1 and shows the upper portions of the jar in contracted position.

Fig. 3 is an enlarged fragmentary View in central longitudinal section as seen on the line 3-3 of Fig. 1 and shows the locking structure in its contracted position.

Fig. 4 is an enlarged fragmentary view in longitudinal section as seen on the line 4-4 of Fig. 1 and shows the jarring mechanism with the parts in their contracted positions.

Fig. 5 is an enlarged fragmentary view in longitudinal section as seen on the line 5 5 of Fig. 1 and shows the hammer and anvil structure in their contracted position.

Fig. 6 is a fragmentary view in central longitudinal section showing the parts previously disclosed in Fig. 2 in their extended positions.

Fig. 7 is an enlarged fragmentary view showing the parts previously disclosed in Fig. 3 in their extended positions.

Fig. 8 is an enlarged fragmentary View showing the parts of the jarring mechanism previously shown in Fig. 4 when the jar is in its extended position.

Fig. 9 is an enlarged fragmentary view showing the parts of the hammer and anvil structure previously disclosed in Fig. 5 but with the parts in their extended positions.

Fig. 10 is a view in longitudinal section and elevation showing the split nuts of the jarring mechanism and a portion of the threaded mandrel for actuating the same.

Fig. 11 is a view in transverse section through the lock structure as seen on the line H-II of Fig. 3.

Fig. 12 is a view in transverse section through the lock structure as seen on the line I2-I2 of Fig. 7 and shows the engaging position of the splined portion thereof.

Fig. 13 is a view in transverse section through the jarring mechanism as Seen on the line |3--l 3 of Fig. 4 and shows the relation of the split nut segments to the mandrel.

Fig. 14 is a View in transverse section as seen on the line lli- HiI of Fig. 4 and shows the means whereby the split nuts are disposed in driving relation tothe mandrel.

Fig. 15 is a view in transverse section as seen on the line |5-l5 of Fig. 8 and shows the split nut structure.

Fig. 16 is a diagrammatic view showing the developed surface of the locking head with the parts in locked position, as indicated in Fig. 3 of the drawing.

Fig. 17 is a diagrammatic view similar to Fig. l5 and showing the locking head rotated preparatory to release.

Fig. 18 is a diagrammatic view similar to Fig. 15 showing the locking head released, thus placing the tool in condition for jarring operations.

.Referring more particularly to the drawings, il! indicates a fragmentary portion of a drill string by which a well jar is supported. This member' is formed with a pin I I -which is threaded into a box portion I2 of a coupling member I3. The lower end of the coupling member I3 is formed with a central cylindrical threaded bore I4. At a point between the box portion I2 and the threaded bore I4 an internal shoulder I5 is formed having a central opening IS through it. An upper drive mandrel I1 is provided and has an upper end of reduced diameter, as indicated at I8, which is threaded into the bore I4. A shoulder I3 is formed on the mandrel I1 and abuts against the end face of the coupling I3. The lower end of the mandrel I1 is formed with a length of enlargeddiameter. Within this portion-a bore 2| is formed. This bore is threaded at'22. -Directly above the bore 2I is -a-bore'23 of reduced diameter. This bore extends fora distance sufficient to provide a suitable bearing surfacefor a-purpose to be hereinafter described. Above the bore 23 is a-counterbore 24. The counterbore 24 extends to the top of the drive mandrel I1 and is threadedatv 25. Astuiiing glandZ is threaded into vthe counterbore and acts against suitable packing 21. A central mandrel ES'extends through the Ydrive mandrel` Iland is of a diameter substantially agreeingwith'the bore 23 in the drive mandrel. The lupper -end of the central mandrel extends through the opening I6 in thecoupling I3"and-to aV height above -the shoulder I5 when the parts-are locked incontracted position as shown'inligs. 2 to 5. This mandrel has a circulating passageway 23 through it. The lower end of the'central mandrel 28 hasan enlarged 4portion 28 which is disposed within the enlarged counterbore portionl 2I of the drive mandrel. A threaded pin'30 isvformed at the lower end of thecentral mandrel 28 and extendsl into a threaded bore30' of a splined central mandrel head 3l. This head `is formed with a plurality of splines` 32 extending longitudinallyand arranged around Vits circumference. The-splined portion occurs-within a counterbore 33 of a drive mandrel extension 34. A threaded pin 35 is formed at the lower end of the splined head 3|. This pin extends into a threaded bore 35 of a tubular central mandrel extension 31. The lower end of the drivemandrel extension v34 is'formed with a threaded counterboreA 38 which receives the upper Vthreaded end of a locking head A353. The locking head 39 is thus rigidly secured to the drive mandrel extension -34 and moves pwith it.I This head is formed with acentral bore 411` which receives the `tubular` central mandre1 extension 31 and upon which the head 39 reciprocates. The locking head 39 is formed at -its Vupper -end with a Vseries ofv inwardly extending splines 4I and intermediate keyways 42 formed in the vwall of the upper portion of the bore Ml. Thus, when the locking head 39 is in its uppermost position splines 32 of the head 3| will be received within keyways 42 and the head 39 will be keyed to rotate withthe-head 3l, and when it is in its lowered position it will be freelyrotatable withY relation-to the tubular cen- I tral mandrel extension' 31. -As shown diagrammatically in Figs. 16 to 18 of the drawings, it will `be seen that the outer circumference of the locking head 39 is formed with an upper continuous cylindrical portion 43 and a pairof diametrically opposite arcuate segments 44. The cylindrical portion 43 provides a `continuous shoulder 45 around the ,locking head, which shoulder is spaced a predetermined distance from the upper faces 46 of the arcuate segments 44.

4 Midway the length of each of the faces 46 of the arcuate segments .and extending between these faces and the shoulder 45 are lugs 41. These lugs substantially span the space between the shoulder and the faces 4S for a purpose to be hereinafter described.

The locking head 39 is disposed within a counterbore 48 formed in the upper end of a lock housing 49. Thelock housing 49 has a central cylindricalbcre 5I) through which the tubular mandrel extension 31 extends. The upper end of the. lock housing counterbore 48 receives the lower end ofthe drive mandrel extension 34. The outei circumference of the upper end of the lock housing 49 is externally threaded at E3 and extends into a-threaded bore 5I formed in the -lower end of a tubular lock housing top 52 which encloses the upper drive mandrel I1 and may reciprocate with relation thereto. The upper drive mandrel I 'I is formed with a reduced diameter-section53 which terminates in a shoulder 54. This provides a-fluid space 55 between -the upper drive mandrel I'I-and the lwall of the 'lock housing top 52. Vent openingsEB-extend through this wall to prevent fluid lock of the relative moving parts. This will insure free relative longitudinalmovement between the locking head 39 and the lock housing 49 when required.

At the time the well jar is run into the well the locking head 39 and the lock housing 49 areheld against relative longitudinal-movement. 'This is accomplished by providing arcuate lock lugs "51 which extend inwardly from vdiametrically opposite sides'of the counterbore 48 within the lock housing 4S. These lugs are spaced in a plane longitudinally of the locking head 39` which will normally position them between the shoulder 45-and the faces 45. The vertical width of the lugs'is substantially the distance between the shoulder 45 and the faces 4S so that relative rotationbetween the locking head and the loclchousingswill'permit the lugs to slide between the faces and thus prevent relative longitudinal movement between the locking head 39 and the lock housing 4S) while in this interlocked position. The end faces of the lugs 51 are radial and will abut against the radial side faces of the intermediate lugs 41 carried by the locking head 33. The construction and arrangement of these members is particularly disclosed in Fig. ll of the drawing where the arcuate lugs 51 are shown as being disposed in locking position between thev shoulder45 vand the faces 46 and abutting against the radial faces of the intermediate lugs 41. `This position is also shown in the diagrammatic Fig. 16.

The bore 53 within the lock housing 49 is formed with a counterbore 58 which occurs beneath the counterbore 48. The counterbore 58 receives packing 59 and a stuiing gland Bil which is threaded into the upper end of the bore to create a fluid seal between the central mandrel extension 31 andthe lock housing 49. At the lower end of .the bore E3 within the lock housing 49 is a counterbore 6I which receives a helical engaging spring 62. This spring circumscribes the central mandrel extension 31 and is engaged at its lower end by a retaining member 63 which has a. cylindrical portion fitting within the counterbore 6I and an inturned end flange 64 against which the lower end of the spring 62 rests. Longitudinal slots vIE5 in the cylindrical portion of the member '63 receive retaining pins 65 which permit the retaining member63 to move upwardly while the spring is being compressed and will limit the amount of expansion of the spring. The lower end of the lock housing 49 is externally threaded at 61 and extends into a threaded bore 68 formed in the end of a drive housing 69. The drive housing is cylindrical and tubular and has a central bore carrying a continuous thread l0. The thread 'l0 is here shown as an acme thread of coarse pitch. This thread produces the motion for a jarring stroke of the tool as will be hereinafter described. Before explaining the jarring structure it is desirable to describe the other elements making up the tool and its connection with the object to be jarred.

At the lower end of the drive housing 69 is a threaded bore which receives a threaded pin section 'l2 of an anvil sub '|3. The sub 'I3 is a cylindrical member internally threaded at its lower end as indicated at 14. The thread 14 receives a pin portion 'f5 of a bottom sub 16. The bottom sub is formed with an externally threaded pin which may be attached to any desired type of ilshing tool. The anvil sub '|3 is formed intermediate its ends with a smooth cylindrical bore 18. The upper end of the anvil sub 13 is formed with a bore of reduced diameter, as indicated at 79. An anvil 8D is thus formed at the upper end of the cylindrical bore 18 and at the beginning of the lower end of the reduced bore 79. Extending through the anvil sub 13 and the bottom sub 'l' is a hammer mandrel 8|. This mandrel is free to slide longitudinally of the bores '|8 and '[9 in the anvil sub 'I3 and a central bore 82 in the bottom sub 16. The central bore 82 is provided with a stuing gland 83 so that the joint between the bottom sub 16 and the lower portion of the hammer mandrel 8| will be fluidtight. Formed around the circumference of the hammer mandrel 3| and at a point midway its length is a hammer 84. This hammer is of a din ameter to have a sliding t within the bore 18 of the anvil sub and is formed with a hammer face 85 which is opposed to the anvil face S0 so that the hammer and anvil may have impact when the well jar is in operation. A face 86 is formed at the lower end of the hammer 84 and is opposed to an end face 8l on the bottom sub 16. An intermediate space 88 occurs between the face 86 and Bl. This space is substantially duid-tight and is free of liquid. At the upper end of the bore 19 within the anvil sub is a Counterbore l2 at the bottom of which packing is mounted as indicated at 8S. This is for the purpose of making a fluid-tight connection between the bore 'I9 and the circumference of the hammer mandrel 8|. Thus the space Sil occurringbetween the anvil face 80 and the hammer face 85 will be fluid-tight and substantially free of liquid. Counterbore 'l2' is internally threaded and receives an externally threaded member 13', which bears against the packing 89.

The upper end of the hammer mandrel 8| is formed with a threaded Counterbore 90. This Counterbore receives the lower end of a tubular main drive mandrel 8|. The upper end of the main drive mandrel Bl is formed with a threaded pin section 92 which extends into a threaded Counterbore 93 in the lower end of the central mandrel extension 3l. Thus it will be seen that the central mandrel 28 has a threaded connection to the splined head 3| and that the lower end of the splined head has a threaded connection with the central mandrel extension 3l. The

drel 8|, all of which elements when assembled produce a continuous rigid tubular structure extending centrally through the well jar. The upper end of the tubular structure is slidably mounted in the upper drive mandrel which is rigidly secured to the string l0 through the coupling |3, while the lower end of the rigid tubular structure is slidably mounted in the bottom sub '.'6 which is rigidly secured to the iishing tool. Thus, the structure rigidly connected to the sub I3 and the structure rigidly connected to the fishing tool have relative longitudinal movement both with respect to the rigid tubular structure and with respect to each other. This movement is utilized in producing the jarring action and in creating the jarring impact between the hammer face and the anvil face 8c.

The present tool is designed to create jarring impact by a continuous rotation of the sub i3 and the assembled mandrel string connected therewith. The structure for producing this result is illustrated in detail in Figs. 4, 8, l0, 13, 14 and l5 of the drawings. Here it will be seen that the main drive mandrel 9i carries a top spreader bushing 94 and a lower spreader bushing 95. These bushings have a central cylindrical bore through which the main drive mandrel 9| has a sliding fit. The bushings at their outermost ends are each formed with an annular flange 95. The annular ilange of the bushing 94 abuts against the end of the central mandrel extension 3? when the device is as shown in Figs. 2, 3, 4 and 5. The flange 3S of the lower spreader bushine S5 is spaced from the stop ring 'i3' of the anvil sub 'i3 in such position of the parts. Formed around the circumference of each of the bushings and disposed in opposite relation to each other is a series of circumferentially extending teeth 91 which are of the buttress type although they do not form a continuous thread. In the drawing these teeth are shown as having horizontal faces 98 and inclined back faces 99. The opposing ends of the

spreader bushings

94 and 95 are spaced a distance from each other by actuating ping Hill. These pins, as shown in Figs.

14 and l5 of the drawings, are disposed at 120 to each other, and as shown in Fig. l5 of the drawing the actuating pins extend longitudinally of and rest against the cylindrical face of the main drive mandrel el. lt will be seen that the spreader bushings abut against the opposite ends of the pins so that the bushings and the pins will move in unison longitudinally of the main drive mandrel. Formed upon the circumference of the main drive mandrel 9| and spaced longitudinally of the mandrel are segmental lugs lill. These lugs are indicated in Fig. 14 of the drawing where it will be seen that they have an arcuate outer face and that they are separated by grooves |82 which have parallel faces |63. The parallel faces are spaced equidistant upon opposite sides of the radial center line of the grooves. The lugs are formed with cylindrical bores |434 which extend longitudinally of the lugs and parallel to the axis of the main drive mandrel 9|. These bores are of a size suitable to receive the actuating pins iil and allow them to reciprocate as the tool operates.

Mounted upon the spreader bushings and designed to embrace the bushings is a split nut structure indicated at it. This structure its between the annular flanges :it on the

spreader bushings

94 and 95 and is of a length shorter than the distance between the opposed faces of the I flanges 9E by an amount as represented approximately vby. the'distance Ybetween the faces 990i the teeth 91. This will allow the split nut to have longitudinal movement relative to the spreader bushings 94 and'95'as will be hereinafter described.` The splitA nutcomprises nut segments |06 indicated in Fig. 15 of the drawings. vThese segments are arcuate and their opposite edges lie in a Iplane substantially tangent tothe circumferenceof the main drive mandrel 9|. Each of the segments is formed with two portions of reduced width, as indicated in section at |01 in Fig. 14Y of the drawings. The said portions are shown in elevation in Fig. of the drawings. These portions t in the grooves |02 occurring Vbetween the lugs |0|. Thus, it will `be seen that the split nut segments are held against longitudinal movement with relation to the main drive mandrel 9| Awhile the

spreader bushings

94 and 95 may have longitudinal movement within the nut segments. The nut segments are held yieldably in position around the spreader bushings by annular coil springs |08 whichV lie within grooves |09 occurring at the opposite ends of the segments.

The split nut segments are formed throughout their length with a continuous coarse thread ID. The vthread is cut so that it will be in its normal position when the split nut is expanded, as will be hereinafter described. That is to say that when the split nut is expanded to its normal pitch diameterthe threads on the outer surfaces thereof 'will be in helical continuity, even though there'will be a space occurring between the contiguous edges of the nut segments, at which time the side walls |93 of the grooves |02 will guide the nut segments |00 so that they will move radially.

The drive housing 59 is formed with a central bore in which is cut the continuous helical thread 10. This thread is of the same pitch and tooth contour as the thread sections on the nut segments |06. Thus, when the nut segments are moved outwardly they will engage the thread 10.

The inner arcuate faces of the nut segments |06 are formed with annular teeth which agree in sectional contour with the teeth' 91 formed on the

spreader bushings

94 and 95. By reference to Fig'. 4 of the drawing it will be seen that these teeth are shown as meshing with each other` and that the relatively square faces 98 of the teeth 91' abut against faces 98 ofthe teeth and that furthermore, the inclined faces 09 of the teeth 01 lie against the inclined faces 99 of the teeth Attention is also directed to the fact that the ends of the teeth 91 and I|| are blunt and flat longitudinally so that faces |2 of the teeth 91 may be contacted by faces I I2 on the teeth when the nut segments |00 are in their expanded positions, as shown in Fig. 8 of the drawing. In this position the thread l0 on the exterior of the nut segments |96 is in mesh with the thread`10 within the drive housing 69.

In operation of the present invention the coupling I3 is connected to a supporting string of pipe I0 and the bottom sub 15 is connected with certain fishing tools not shown in the drawing. The well jar is then placed in a position so that the parts connected with the string and those connected with the fishing tool are held against relative longitudinal movement by positioning the arcuate lugs' 51 between the continuous shoulder 45 and the faces 46 of the arcuate segments 44, as shown in Fig. 16 of the drawing. This is done by rotating the lock head 39 in a counter-clockwise direction, as indicated `by the larrow a in Fig. l1 of the drawing, with the result that the arcuatelock lugs 51 will labut against the contiguous faces of the intermediate lugs 41 on the locking head 39. At this time the splines 32 on the splined head 3| will be disengaged, the rigid tubular mandrel assembly will have `limited slidable motion and the drive housing 69 will be held against longitudinal movement with relation to the locking head 39-and the mandrel structure of which the upper drive mandrel |1 forms a part. It will also be noted as shown in-Figs. 2, 3, 4 and 5 of the drawing that in the locked position the tubular mandrel structure is in its lowerl position with respect to the drive Ahousing and'its rigidly connected parts, so that the hammer is at the bottom of the space'90 and the top spreader bushing abuts against the shoulder of the-central mandrel 31 so that the bushings are elevated with respect to the nut segments, andthe -teeth 91 ofthe spreader -bushings 94 and 95 'are in mesh with the complementary teeth formedon the inner faces of the split nut segments |06. These teeth are held yieldably in this meshed position by the contractive laction of the springs |08.

After the object to be jarred has been engaged by the fishing tool carried at the lower end of the sub 13 it is necessary to unlatch the jar and to place a strain on the object. This unlatching action is produced by rotation of the suporting string i0, the sub I3, and the upper drive mandrel E1. The action will also rotate the locking head 39 so that the arcuate lock lugs 51 will move circumferentially ofthe axis of the jar until they register with arcuate openings44 occurring between the radial edges ofthe arcuate segments 44. This `position is shown in'Fig. 1'1 of the drawing. When a strain is then placed on the supporting string I0 the arcuatef'lock'lugs 51 will remain substantially 'stationary and the arcuate segments 44 willpass upwardly :between the lock lugs'51 to an unlatched iposition. As this movement takes place the splines 32 pass into the keyways 42 in the locking head 39 and thus key the upper drive mandrel |1 to the central mandrel extension 31 so that the main drive mandrel 9| may be rotated within the drive housing 69. Coincident with the upward movement of the locking head to engage the splines'32 the upper end of the drive mandrel extension' 34 will strike the enlarged portion 28 of the central mandrel 28 to lift the tubular mandrel assembly. As the main drive mandrel is drawn upwardly incident to this movement the flanged end 96 of the spreader bushing 94 will encounter the end 64 of the springretaining member 93. The spring 62 will thus resist upward movement of the spring retaining member and will tend .to resist upward movement of the spreader bushing 94. .At this same time the split nut structure |05 will be moved positively with the main drive mandrel 9| due to the engagement of the lugs |0| with the split nut segments. This will cause the faces v99 of the teeth to ride up on the inclined faces 99 of the teeth 91 of both the

spreader bushings

94 and 95. In turn the split nut segments |06 will move radially to positions where the teeth ||0 will be held in threaded engagement with the teeth 10 of the drive housing'69. It should be noted that during the initial upward movement of the string, coupling, upper and main `drive mandrels, the bottom sub, anvil sub and drive housing remain stationary. Thus the hammer 84 will be raised in the space 90. During this time the supporting string l0 is rotating and imparts rotation through the coupling 3, the upper drive mandrel Il and the tubular mandrel extension 3l to the main drive mandrel 9|. The pitch inclination of the teeth 'IU and Il!) are such as to insure that the main drive mandrel 9| will be placed under tension. Since the drive housing is relatively stationary, the continued rotation of the nut segments with the main drive mandrel will cause the tubular mandrel assembly to move downwardly by the threaded feed operation of the nut within the housing. Such movement will retract the hammer downwardly in the space 9D. After predetermined downward movement the flange 96 of the lower bushingr 95 will strike the stop ring 12', the adjustable setting of which above the end of the pin section l2 determines the blow, and the bushings will thus be forced upwardly in the nut segments. The nut segments I B will ride oi the end faces H2 of the teeth I l l. This will allow the springs |08 to draw the lock nut segments |06 to retracted positions and the thread l I0 out of engagement with the thread l0 in the lock nut housing. In view of the fact that the drive mandrel structure is under tension the hammer 84 will instantly move upwardly and its face 85 will strike the anvil face Bil with an impact blow represented by the stretch in the supporting pipe l0 plus the stretch produc@ by the pitch angle of the threads 'l0 and H0. As soon as the blow has been delivered the drive mandrel and associated parts will resume their original position and the spring 62 will tend to yieldably urge the

spreader bushings

94 and 95 to a setting position again. It is obvious therefore that continuous driving rotation of the supporting string will cause a succession of impact blows to be created between the hammer and the anvil so long as the structure is rotated.

Attention is directed to the fact that the space occurring between the lower end of the lock i housing 49 and the upper end of the anvil sub 13, as indicated at l l5, will be filled with oil. This oil is introduced through an opening Il closed normally by a threaded plug Ill. By this arrangement the threaded parts will be lubricated at all times.

It will thus be seen that the present structure comprises a compact well jar which may be latched in a retracted position for entry into a well bore, the latching insuring that the iishing tool may be eiiciently manipulated from the surface of the ground, after which the supporting string may be manipulated to unlatch the tool and to establish a, driving connection between the supporting string and the main drive mandrel which carries an anvil, the said structure being operated Iby relative rotation of the main drive mandrel and the housing whereby a succession of jarring blows of a desired magnitude may be created while the drill string rotates continuously.

While we have shown the preferred form of our invention as now known to us, it will be understood that various changes may be made in combination, construction and arrangement of parts by those skilled in the art, wtihout departing from the spirit of the invention as claimed.

Having thus described our invention, whatwe claim and desire to secure by Letters Patent is:

l. A rotary well jar comprising a tubular mandrel, means on the lower end of the tubular mandrel for connecting the same to a section ci drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and reciprocable therein, a hammer xed to the second mandrel, an anvil iixed to the tubular mandrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, a iirst threaded member carried 'by said tubular mandrel, a second threaded member mounted on said second mandrel for outward movement for engagement with said first threaded member and adapted when rotated to thread downwardly on said first threaded member to cause separation of the hammer and anvil and stretching of the drill string and adapted to be moved inwardly to be disengaged from the rst threaded member to release said second mandrel and allow contraction of the drill string and impact between the hammer and anvil, and means responsive to longitudinal movement of the second mandrel including a cam for causing periodic outward and subsequent inward movement of the second threaded member to cause corresponding periodic impact between the hammer and the anvil.

2. A rotary well jar comprising a tubular mandrel, means on the lower end of the tubular mandrel for connecting the same to a section of drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and reciprocable therein and adapted to be connected to a drill string, a hammer `fixed to the second mandrel, an anvil fixed to the tubular mandrel and normally arranged oontiguously with respect to said hammer, means for rotating said second mandrel, a rst threaded member carried by said tubular mandrel, a second threaded member mounted on said second mandrel for outward movement for engagement with said first threaded member and adapted when rotated to thread downwardly on said rst threaded member to cause separation of the hammer and anvil, and stretching of the drill string and adapted to be moved inwardly to be disengaged from the nrst threaded member to release said second mandrel and allow contraction of the drill string and impact between the hammer and anvil, means responsive to longitudinal movement of the second mandrel and including a cam for causing periodic outward and subsequent inward movement of the second threaded member to cause periodic impact between the hammer and anvil, means carried by the tubular mandrel for moving the cam to camming position, and means carried by the tubular mandrel and spaced from the last named means for moving the cam to inoperative position.

3. A rotary well ia-r comprising a tubular mandrel, means on the lower end of the tubular mandrel for connecting the same to a section of drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and reciprocable therein and adapted to be connected to a drill string, a hammer fixed to the second mandrel, an anvil fixed to the tubular mandrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, a first threaded member carried by said tubular mandrel, a second threaded member mounted on said second mandrel for outward movement for engagement with said rst threaded member and adapted when rotated t0 thread downwardly on said rst threaded member to cause separation of the hammer and anvil, and stretching of the drill string and adapted to be moved inwardly to be disengaged from the nrst threaded member to release said second mandrel and allow contraction of the drill string and impact between the hammer and anvil, means 'including a cam for causing periodic outward and subsequent inward movement of the second threaded member to cause periodic impact between the hammer and anvil, said cam being mountedY on said second mandrel for limited longitudinal sliding movement relative thereto in one direction to cam the second threaded member outwardly and limited longitudinal movement in the opposite direction to allow inward movement of the second threaded member, means for urging inward movement or the second threaded member, means carried by the tubular lmandrel for moving the cam to camming position, and means carried by the tubular mandrel and spaced from the last named means for movingv the cam to inoperative position.

4. A rotary well jar comprising a tubular mandrel, means on the lower end of the tubular mandrel for connecting the sa-me to a section of drill pipe or the like, a second mandrel disposed within the` tubular mandrel and rotatable and reciprocable therein and adapted to be connected to a drillstring, a hammer xed to the second mandrel, ananvil xed to the tubular mandrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, -a `first threaded `member carried by said tubular mandrel, a second threaded member mounted on said second mandrel for outward movement for engagementV with said first threaded member andadapted when rotated to thread downwardly on said rst threaded membervto cause separation of the hammer an anvil',i and stretching of the drill string and adapted to be moved inwardly to be disengaged fromrthefirst threaded member to release said second mandrel and allow contraction of the drill stringiand impact between the hammer and anvil,,means including a cam for causing periodic outward and subsequent inward movement of the second,r threadedY member to cause periodic impact between the hammer and anvil, said cam being,mount-eden saidsecond mandrel for limiterdA longitudinal sliding movement relative theretoingone direction to cam the second threaded member` outwardly and limited longitudinal movement in the` opposite direction to allow inward-movement; of thesecond threaded member, -means for urginginward movement of the secondthreadedmember,v means carried by the tubular mandrel foi-*moving the cam to camming position, means carried by the tubular mandrel and spaced from the last namedV means forv moving, the cam to inoperative position, means; attachable to a drill string and connected to;said second mandrel; for moving said second mandrelto -a position to cause an initial engage- -mentfof sai dlast named means and said cam to cause lan, initial engagement -betweenthe threaded,members.v

5. A rotary Iwelljarcomprising a tubular mandrel,- means onpthelower end of the tubular mandrei-for connecting -the'sarne to a section of drill pipeor the like, a second mandrel disposed withinthe tubular mandrel androtatable and'reciprocable therein andadapted'to be connected to a drill string, a hammer xedto the second mandrel, an anvil xed tothe tubular mandrel and normallyv arranged; contiguously with respect to said .hammerf-meansi-y for rotating said second mandrel, a rst threaded member carried by said tubular mandrel, a second threaded member mounted1 on .saidsecond mandrel for outward movement for engagement with said rst threaded member and adapted whenr rotated to thread downwardly on said, first threadedrmember to cause separation of the hammer and anvil, and stretching of the drill string and adapted to be moved inwardly to be disengaged from'the iirst threaded member to release said second mandrel and allow contraction of the drill string and impact between the hammer and anvil, means including a cam for causing periodic outward and subsequent inwardmovement of the second threaded member to cause periodic impact between the hammer and anvil, said cam being mounted on said second mandrel for limited longitudinal sliding movement relative thereto in one direction to cam the second threaded member outwardly and limitedA longitudinal movement in the opposite direction to allow inward movement of the second threaded member, means for urging inward movement of the second threaded member, means carried by the tubular mandrel for moving the cam to camming position, means carriedl by the tubular mandrel and spaced from the last named means for moving the cam to inoperative position, means attachable to a drill string and connected to said second mandrel for moving said second mandrel to a position to cause an initial engagement of said last named means and said cam to cause an initial engagementbetween the threaded members and having a driving connection with said second mandrel for rotating the same.

6. A rotary well jar comprising a tubular mandrel, means 0n the lower end of the tubular mandrel for connecting the same to a section of drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and reciprocable therein and adapted to be connected to a drill string, a hammer xed to the second mandrel, an anvil fixed to the tubular mandrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, a first threaded member carried by said tubular mandrel, a second threaded, member mounted on said second mandrel for outward movement for engagement with said iirst threaded member and adapted when rotated to. thread downwardly on said first threaded member to cause separation of theV hammer and anvil, and stretching of the drill string and adapted to be moved inwardly to be disengaged from the' first threaded member to release said second mandrel and allow contraction of the drill string and impact between thev hammer and anvil, means including a cam for causing periodic. outward and subsequent inwardmovement of vthesecond threaded member tocause. periodic impact' be-v tweenthe hammer and anvil, said cam being mounted on said secondmandrel forlimited longitudinal-sliding movement relative thereto in onev direction to cam the second threaded member outwardly and limited longitudinal movement in the opposite direction to allow inward movement of the second threaded member, means for urging inward movement. of the vsecond threaded member, means carried by v`the.tu.l bular. mandrel for. moving the. camto camming. position, means ,carried .by the tubular mandrel and spaced fromthe last named means for moving the, cam. to inoperative position, means attachable to a drill string and connected to said -second mandrel for moving said second mandrel to a position rto cause an initial engagement of said last named means and said cam to cause an initial engagement-between the threaded members and having a driving connection with saidsecond mandrel for rotating the 13 same and having a disconnectible driving connection with said tubular mandrel.

7. A rotary well jar comprising a tubular mandrel, means on the lower end of the tubular mandrel for connecting the same to a section of drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and recip- -rocable therein and adapted to be connected to a drill string, a hammer fixed to the second mandrel, an anvil xed to the tubular mandrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, a rst threaded member carried by said tubular mandrel, a second threaded member mounted on said second mandrel for outward movement for engagement with said iirst threaded member and adapted when rotated to thread downwardly on said first threaded member to cause separation of the hammer and anvil, and stretching of the drill string and adapted to be moved inwardly to be disengaged from the rst threaded member to release said second mandrel and allow contraction of the drill string and impact between the hammer and anvil, means including a cam for causing periodic outward and subsequent inward movement of the second threaded member to cause periodic impact between the hammer and anvil, said cam being mounted on said second mandrel for limited longitudinal sliding movement relative thereto in one direction to cam the second threaded member outwardly and limited longitudinal movement in the opposite direction to allow inward movement of the second threaded member, means for urging inward movement or the second threaded member, means carried by the tubular mandrel for moving the cam to camming position, and means carried by the tubular mandrel and spaced from the last named means for moving the cam to inoperative position, means attachable to a drill string and telescopically engaging both said mandrel-s and movable relative to the mandreis to one position to drivingly engage one mandrel and to another position to drivingly engage the other mandrel.

8. A rotary well jar comprising a tubular mandrel, means on the lower end of the tubular mandrel for connecting the same to a section of drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and recipi'ocable therein and adapted to be connected to a drill string, a hammer xed to the second mandrel, an anvil xed to the tubular mnadrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, a rst threaded member carried by said tubular mandrel, a second threaded member `mounted on said second mandrel for outward movement for engagement with said nrst threaded member and adapted when rotated to Vthread downwardly on said first threaded member to cause separation of the hammer and anvil, and stretching of the drill string and adapted to be moved inwardly to be disengaged from the rst threaded member to release said second mandrel and allow contraction of the drill string and impact between the hammer and anvil, means including a cam for causing periodic outward and subsequent inward movement of the second threaded member to cause periodic impact between the hammer and anvil, said cam being mounted on said second mandrel for limited longitudinal sliding movement relative thereto in one direction to cam the second threaded member outwardly and limited longitudinal movement in the opposite direction to allow inward movement of the second threaded member, means for urging inward movement of the second threaded member, means carried by the tubular mandrel for moving the cam to camming position, means carried by the tubular mandrel and spaced from the last named means for moving the cam to inoperative position, means attachable to a drill string and telescopically engaging both said mandrels and movable relative to the mandrels to one position to drivingly engage one mandrel and to another position to drivingly engage the other mandrel, and connected to said second mandrel for moving said second mandrel to a position to cause an initial engagement of said last named means with said cam to cause an initial engagement between the threaded members.

9. A rotary well jar comprising a tubular mandrel, means on the lower end or the tubular mandrel for connecting the same to a section of drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and reciprocable therein and adapted to be connected to a drill string, a hammer xed to the second mandrel, an anvil fixed to the tubular mandrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, a first threaded member carried by said tubular mandrel, a second threaded member mounted on said second mandrel for outward movement for engagement with said nrst threaded member and adapted when rotated to thread downwardly on said first threaded member to cause separation of the hammer and anvil, and stretching of the drill string and adapted to .be moved inwardly to be disengaged from the rst threaded member to release said second mandrel and allow contraction of the drill string and impact between the hammer and anvil, means including a cam for causing periodic outward and subsequent inward movement of the second threaded member to cause periodic impact between the hammer and anvil, said cam being mounted on said second mandrel for limited longitudinal sliding movement relative thereto in one direction to cam the second threaded member outwardly and limited longitudinal movement in the opposite direction to allow inward movement of the second threaded member, means for urging inward movement or" the second threaded member, means carried by the tubular mandrel for moving the cam to camming position, means carried `by the tubular mandrel and spaced from the last named means for moving the cam to inoperative position, means attachable to a drill string and teiescopically engaging both said mandrels and movable relative to the mandrel to one position to drivingly engage one mandrel and to another position to drivingly engage the other mandrel and having limited upward movement with respect to said second mandrel to enable lifting of the second mandrel to cause an initial engagement of the cam and said last named means and thereby an initial engagement `between said threaded members.

10. A rotary well jar comprising a tubular mandrel, means on the lower end of the tubular mandrel for connecting the same to a section of drill pipe or the like, a second mandrel disposed within the tubular mandrel and rotatable and reciprocable therein and adapted to be connected to a drill string, a hammer nxed to the second mandrel, an anvil nxed to the tubular aersgree `15 mandrel and normally arranged contiguously with respect to said hammer, means for rotating said second mandrel, a first threaded-'member carried by said `tubular mandrel; a second threadedv member mounted on said second mandrel for outward movement for engagement with said rstthreaded member and adapted'. when rotated to thread downwardly .onv said rst threaded member to cause separation of the hammer: and anvil, andv stretching ofLthedrill string and adapted to bermoved. inwardlyto .be disengaged from the rst threaded memberto release said second. mandrel and allowfcontraction of the drill string and impact between. the hammer and. anvil, means .includinga camfor causing periodic outward and subsequent. inward movement of the second. threaded member yto cause periodic impact between the hammerand anvil, said cam. being mounted on said second mandrel for limited longitudinal-sliding movement. relative vtheretofin one direction-tocara the second threadedmember outwardly and limited longitudinal movementI .in the .opposite direction to allow inward movementof .the secondthreaded member, means for urging. inward movement of the second threaded member, meanscarried by thetubular mandrel for moving thecam tocamming` position, means 'carried by the tubular mandrel and spaced from vthe last .named means' for moving the .cam .to .inoperative .'position, -means attachable lto a drill string. and telescopically engaging bothsaidmandrels and .movableupwardly relative tothe mandrels toestablisha driving connectionto said second mandrel and movable downwardly relative -to Asaid mandrel to establishA a driving connection with-saidtubular mandrel and having limited upward movement relative to said second mandrel to enable lifting ofthe second mandrel -to cause an initialengagement of the cam and said last named means and .L

rotaryand-axial'movement vand adaptedv to-be connected to a'supporting drill string anda member to be jarredv respectively, a hammer and-an anvil xed one to each of the mandrels' and Abeing contiguously disposed'in axial registry with respect to one another; means responsivetorotation ofthe first mandrel relative to the second mandrel for causing downward'I movement of the first mandrel relative toY the' secondl mandrel'to stretch the drill stringand separate the yhammer and anvil, said means comprising a continuous thread formed on'one mandrelr anda mating threaded member engaging saldi continuous thread and being mounted on said other-.mandrel for radial separating movement for disengagement from the continuous thread on said one mandrel to allowthe drill string'tocontract to cause a violent impactbetween the hammer-and anvil, and means responsive-to a predetermined amount of downward movement of theE first mandrel relative to the second mandrelvto causea separation of thev threaded connection between the mandrels and being operable upon a return` of the first mandrel to its upward position to cause a re-engagementof Y the threaded memberwith `the continuous thread, whereby a seriesof violent jars will be produced upon continuousrotation of the first mandrel relative v'tothe second mandrel.

12. A rotary well jar,.-comprising inst-and second mandrels coaxially arranged for relative rotary and axial movement'. and adapted to be connected to a supporting drill string and a member to be jarred respectively,- a hammer and'.v an anvil xed' one to eachl of theimandrels andbeing contiguously disposedH in axial l registrywith7 vrespect toone another, meansy responsive' 'torotation of.' the first mandrel relative to thesecond mandrel for causing downward movement'o'fthe first mandrel relative to the -second mandrel' to stretch the drill string and'separate the hammer and anvil, said. means comprising a thread formed on. one mandrel anda mating threaded'member engaging saidthread and being mountedy onxsaid other mandrel for radial separating movement for4 disengagement from. said thread. to allowthe drillzstring to contract 'and' causea violentrimpact betweenthe hammer and anvil, and means responsive' to a predetermined amount. of "downfward movementof the; first mandrel relative to the. second mandrel' to cause a radial lsepara-- tion of the threaded connection betweenthe mandrel" and being operable upona return of the iir'st mandrel to its upward. position. to'cause a re-engagement; of .theA threaded member' with .said thread,.whereby a series of violent jars canberobtained upon continuous rotationof the first mandrel relative to the' second mandrel..

13. A rotary welljancomprising rst and'. second mandrels'.l coaxially arranged for relative rotary and axial movement and adaptedi tobe connected toa supporting. drill string and. aI member to be jarredV respectively, a hammer and' an anvilv xed one to each of the mandrelstan'd be"- ing contiguously disposed in axial registryV with respect to one another, means responsive to rotation of the iirst mandrel relative to the second mandrel for causing downward movement of the first mandrel relative tothe second mandrel to stretch the drill string andseparate the hammer and anvil, said means comprising a continuous threadformed on one mandrel and a mating threaded member engagingV said. continuous thread. and being mounted'on said other mandrel'gfor radial separating movement for dischgagement from the continuous thread on saidv one mandrel to allow thedrill stringato contractl to cause a violent impactbetween the hammer. and anvil, and means responsive to av predetermined amount of .downwardmovement of the first' mandrel relative to the second mandrel tocausea separation of the threaded connection between the mandrels and being operable upon-a return of the rstimandrel to its upward positionto cause a re-engagementA of the threadedmember withthe continuousv thread, whereby a series of violent jars will be produced upon continuous rotation of the first' mandrel relative to the' second mandrel, the last-named'means including spring means urging radial disengagementl Vof" the threaded member from lsaid continuous thread.

14.Y A rotary well jar, comprising rst and second mandrels coaxially arranged for relative rotary and axial movement and adapted to be con'- nected' to -a supporting drillrstring and a member to be j arred respectively, a hammer and ananvil xedone to each of -the mandrels and'beingv contiguously-disposed in axial registry' with respect to'one another, means -responsivelto rotation of the first mandrel relative'I to the second mandrel for causing downward movement of the r'st mandrel relative to the second mandrel to stretch the drillv string and separatethe hammerl and anvil, said means'- comprising a threadformedfon one mandrel and a mating threaded member 'engaging said thread and being mounted on said other mandrel for radial separating movement for disengagement from said thread to allow the drill string to contract and cause a violent impact between the hammer and anvil, and means responsive to a predetermined amount of downward movement of the first mandrel relative to the second mandrel to cause a radial separation or the threaded connection between the mandrel and being operable upon a return of the first mandrel to its upward position to cause a re-engagement of the threaded member with said thread, whereby a series of violent jars can be obtained upon continuous rotation of the rst mandrel relative to the second mandrel, the lastnamed means including spring means urging disengagement of the threaded member from said thread and cam means for causing re-engagement of the threaded member with said thread.

l5. A rotary well jar, comprising first and second mandrels coaxially arranged for relative rotary and axial movement and adapted to be connected to a supporting drill string and a member to be jarred respectively, a hammer and an anvil fixed one to each of the mandrels and being contiguously disposed in axial registry with respect to one another, means responsive to rotation of the first mandrel relative to the second mandrel for causing downward movement of the first mandrel relative to the second mandrel to stretch the drill string and separate the hammer and anvil, said means comprising a continuous thread formed on one mandrel and a mating threaded member engaging said continuous thread and being mounted on said other mandrel for radial separating movement for disengagement from the continuous thread on said one mandrel to allow the drill string to contract to cause a violent impact between the hammer and anvil, and means responsive to a predetermined amount of downward movement of the rst mandrel relative to the second mandrel to cause a separation of the threaded connection between the mandrels and being operable upon a return of the rst mandrel to its upward position to cause a re-engagement of the threaded member with the continuous thread, whereby a, series of violent jars will be produced upon continuous rotation of the rst mandrel relative to the second mandrel, the last-named means including cam means carried by said other` mandrel engageable with an abutment device on said one mandrel to cause engagement of the threaded member and said continuous thread.

16. A rotary well jar, comprising first and second mandrels coaxially arranged for relative rotary and axial movement and adapted to be connected to a supporting drill string and a mernber to be jarred respectively, a hammer and an anvil fixed one to each of the mandrels and being contiguously disposed in axial registry with re spect to one another, means responsive to roton of the rst mandrel relative to the second mandrel for causing downward movement of the rst mandrel relative to the second mandrel to stretch the drill string and separate the hammer and anvil. said means comprising a continuous thread formed on one mandrel and a mating threaded member engaging said continuous thread and being mounted on said other mandrel for radial separating movement for disengagement from the continuous thread on said one mandrel to allow the drill string to contract to cause a violent impact between the hammer and anvil, and means responsive 'G0 a predetermined amount of downward movement of the first mandrel relative to the second mandrel to cause a separation of the threaded connection between the mandrels and being operable upon a return of the rst mandrel to its upward position to cause a re-engagement of the threaded member Awith the continuous thread, whereby a series of violent jars will be produced upon continuous rotation of the first mandrel relative to the second mandrel, the last-named means including spring means urging the threaded member out of engagement with said thread and cam means carried by said other mandrel engageable with an abutment device on said one mandrel to cause engagement of the threaded member and said thread, and subsequently with an axially displaced abutment on said one mandrel to release the threaded member for disengagement from the said thread under the inuence of the spring means.

17. A rotary well jar, comprising flrst and second mandrels coaxially arranged for relative rotary and axial movement and adapted to be connected to a supporting drill string and a member to be jarred respectively, a hammer and an anvil xed one to each of the mandrels and being contiguously disposed in axial registry with respect to one another, means responsive to rotation of the rst mandrel relative to the second mandrel for causing downward movement of the first mandrel relative to the second mandrel to stretch the drill string and separate the hammer and anvil, said means comprising la thread formed on one mandrel and a mating threaded member engaging said thread and being mounted on said other mandrel for radial separating movement for disengagement from said thread to allow the drill string to contract and cause a violent impact between the hammer and anvil, land means responsive to a predetermined amount of downward movement of the rst mandrel relative to the second mandrel to cause a radial separation of the threaded connection between the mandrel and being operable upon a return of the first mandrel to its upward position to cause a reengagement of the threaded member with said thread, whereby a series of violent jars can be obtained upon continuous rotation of the rst mandrel relative to the second mandrel, the lastnamed means including spring means urging the threaded member out of engagement with said thread and cam means carried by said other mandrel engageable with an abutment device on said one mandrel to cause engagement of the threaded member and said thread, and subsequently with an axially displaced abutment on lsaid one mandrel to release the threaded member for disengagement from the said thread under the influence of the spring means.

EDGAR W. BAGNELL. WILBUR F. BETTIS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,778,252 Fentress Oct. 14, 1930 1,895,227 IMcCullough Jan. 24, 1933 2,326,394 Richey Aug. 10, 1943 2,387,682 Richey Oct. 23, 1943 2,389,711 Armentrout Nov. 27, 1945 2,390,714 ,1911115911 Dec. 1l, 1945