US 3853187 A
This tool embodies in a single structure comprising inner and outer telescopically related tubular elements confining a body of operating liquid, a hydraulically retarded up-blow jar, actuated by placing a lifting strain on the drill string, and a simple mechanically retarded down-blow jar actuated optionally be effecting a controlled downward pressure of the drill string on the jar. The operation of the two jar mechanisms are accomplished respectively by upward movement of the outer element in an upper portion of the range of vertical movement between said elements and by a downward movement of said outer element through a lower portion of said range of vertical movement. A clearly cognizable signal is provided for the driller to indicate to him the arrival of said outer element in the starting position at which the driller may elect which type of jarring blow he desires to produce in the immediately following operation of the duplex jar of the invention.
Description (OCR text may contain errors)
Sutliff et al.
1451 Dec. 10,1974
DUPLEX HYDRAULIC-MECHANICAL J AR TOOL Inventors: Wayne N. Sutliff; Jim L. Downen,
both of 2931 Pierce Rd., Bakersville, Calif. 93308 Filed:
 Feb. 7, 1974  Appl. No.: 440,500
 U.S. Cl. 175/297, 175/304  Int. Cl E21b 1/10  Field of Search 175/293, 296, 297, 299, 175/300, 302, 304, 306; 166/178  References Cited I UNITED STATES PATENTS 1,885,043 10/1932 Beck 175/304 X 2,241,477 5/1941 Rasmussen 175/304 X 2,309,872 2/1943 Shaffer et al. 175/304 X 2,621,024 12/1952 Koppl et a1. 175 297 2,659,576 11/1953 Linney 175/297 3,685,598 8/1972 Nutter ..175/ 304 2( 2,721,056 10/1955 Storm 175/297 2,875,983 3/1959 Sutliff.... 175/304 2,963,101 12/1960 Koppl 175/304 x Primary ExaminerDavid Brown  ABSTRACT This tool embodies in a single structure comprising inner and outer telescopically related tubular elements confining a body of operating liquid, a hydraulically retarded up-blow jar, actuated by placing a lifting strain on the drill string, and a simple mechanically retarded down-blow jar actuated optionally be effecting a controlled downward pressure of the drill string on the jar. The operation of the two jar mechanisms are accomplished respectively by upward movement of the outer element in an upper portion of the range of vertical movement between said elements and by a downward movement of said outer element through a lower portion of said range of vertical movement. A clearly cognizable signal is provided for the driller to indicate to him the arrival of said outer element in the starting position at which the driller may elect which type of jarring blow he desires to produce in the immediately following operation of the duplex jar of the invention.
7 Claims, 21 Drawing Figures PATENIEQ SEC 1 0 I974 I saw 10rd 1442.6'. A 112.
H05 I IGMS.
PATENTEU mac 1 01974 DUPLEX HYDRAULIC-MECHANICAL JAR TOOL SUMMARY OF THE INVENTION It is a primary object of the present invention to pro- 2 duce an improved hydraulic oil well jar of the type covered by US. Pat. No. 2,989,132 issued June 20, 1961 to Jim L. Downen of Bakersfield, Calif. The Downen jar has a fixed packer at the lower end of the outer element and a floating packer between the upper ends of said elements for confining operating liquid in the hydraulic chamber of the tool. Splines provided within said chamber transmit torque between said elements and a piston provided on said inner element makes a close sliding fit with a short cylinder extending inwardly from the inner surface of the outer element when in conjunction therewith, a small vertical escape passage being provided in said piston through which liquid can escape from the high pressure lower section of the hydraulic chamber into the low pressure upper section of said chamber while a strain is being placed on the drill string from which the jar is suspended. As said cylinder rises and moves out of conjunction with said piston the remaining liquid in the lower section of said chamber rushes past said piston into the upper section of the chamber resulting in the delivery of an upward jarring blow between impacting surfaces provided respectively on said inner and outer elements.
The return downwardly of the drill string, immediately following for the purpose of resetting the tool to start another jarring operation, may be very rapidly accomplished in the Downen jar by virtue of the fact that while the piston and cylinder are in conjunction in this return movement, a vacuum is formed in the lower high pressure section of the hydraulic chamber which prevents doing any damage to the jar thus permitting the driller to effect what is known as a spudding operation in which the drill string is rammed downwardly in resetting the jar until the jar is completely collapsed thereby delivering a heavy blowto the fish.
Notwithstanding the merit of the Downen jar and the facility with which a down blow may thus be delivered to the fish alternately with the delivery of a snap action blow upwardly to the fish (with the drill string in tension) the type of blow delivered in the spudding action is not nearly as effective as the snap action blow deliverable upwardly by the Downen jar.
It is a further object of the invention to provide a jar of the general type shown in the Downen patent which will offer the driller the option of delivering snap action jarring blows downwardly with the jar as well as upwardly.
It is yet another object of the invention to provide such a jar in which a clear signal will be given the driller in each jar resetting operation which will indicate the arrival of the outer element at a point in its vertical reciprocatory movement relative to the inner element where the driller has the election of initiating a snap action jar operation in either an upward or a downward direction.
It is a yet further object of the invention to provide such a jar tool in which the lowering of the outer element of the tool is temporarily but positively retarded at the point where the restricting cylinder withdraws downwardly from conjunction with the piston on the inner element, thereby giving notice to the driller that the jar has been restored to its intermediate or starting position from which point the driller may exercise with 1 Yet another object of the invention is to provide in said unit an internal male spline sub having heavy integral external annular heads at both its opposite ends, and an axially split female spline sub assembled broadside on the spline section of the male sub and united at one end by an overriding ring and at the other by its screwing into the internally threaded lower end of the outer tubular element of the jar.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 5 inclusive are vertical half sectional views of successive portions of a preferred embodiment of the invention which, taken together, illustrate the parts of the latter disposed in starting position as when beginning an upward or downward jarring operation.
FIGS. 6 to 10 inclusive are a set of similar views illustrating the moment of impact in an upward jarring op eration.
"FIGS. 11 to 15 inclusive are a set of similar views illustrating the moment of impact in a downward jarrin operation. I 1
FIG. 16 is a side elevational view of the split tubular head of the mechanical retarding device of the downjar structure of the invention.
FIG. 17 is a full cross sectional view taken on the line l7l' 7 of FIG. 2 and shows the split head shrinking ring crowning said split tubular head'and the supporting relation of the quadrant-sections of said head with said ring.
FIG. 18 is a full cross sectional view taken on the line 18-48 of FIG. 2 and shows details of the annular valve piston of the invention and its environment.
FIG. 19 is an elevational view partly in section and shown to a reduced scale of a lower portion of the invention embodying in a single unit all the elements performing the spline, hammer and anvil functions of the invention, this view showing said elements on the process of being assembled.
FIG. 20 is an elevational view of FIG. 19 following the completion of said assembly.
FIG. 21 is a cross sectional view taken on the line 2l-2l of FIG. 20 and illustrating the division of the female spline sub of the invention into two halves.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring specifically to the drawings, the invention is shown therein as embodied in a hydraulic oil well jar 25 which includes an outer tubular element 26 and an inner tubular element 27 which are telescopically relatedto each other for relative axial movement in the operation of the jar. As shown in FIGS. 1 to 5 inclusive the tubular element 26 forms a sleeve which houses the jar and is internally threaded at its upper end so as to screw onto an upper jar 'sub 28 which in turn is adapted to scew onto the lower pin 29 of a tubular drill string 30 on which the jar 25 is suspended.
The outer tubular element 26 has an inner bore 31 which slideably contains therein an upper packing member 32 which is recessed for holding internal rings 33 and external 0-rings 34. The lower end of bore 31 terminates with a shoulder 35 located at the upper end of a counterbore 40. A tripping ring 41 fits within the counterbore 40 against the shoulder 35 and is secured in place by screws 42 which are screwed into suitable tapped holes provided in outer tubular member 26 and fit into suitable recesses provided in the periphery of the ring 41. The ring 41 has an inwardly and upwardly beveled bottom cam face 43 which is preferably ground at an angle of 20 with horizontal.
The counterbore 40 presents a smooth cylindrical surface in a short annular area 44 (see FlG. .2) which will be referred to hereinafter as the cylinder of the jar 25. Immediately above and below the cylinder 44, the counterbore 40 is relieved by vertical channels 45 and 46 for a purpose to be made clear hereinafter. One or more suitable tapped holes are provided in the outer tubular element 26 of the jar for use in admitting operating liquid thereto, these holes being closed by filler plugs 47.
The lower end portion 48 of the outer tubular element 26 (hereinafter referred to as the stabilizer sleeve) is secured to said element by heavy tapered threads 49, the male threads of which are formed on a heavy annular internal head 50 provided to extend inwardly from the upper end of said sleeve. Provided on the head 50 to extend inwardly therefrom is a packer 55. Provided in sleeve-48 for a purpose to be made clear hereinafter, are rather ample fluid ports 56 and 7. Stabilizer sleeve 48 has a smooth internal bore 58 and a lower end portion thereof is provided with heavy female internal threads 59. The lower end of stabilizer sleeve 48 has a male taper 60 of about The threads 59 constitute one of the means for assembly of the two halves 61 and 62 of a female spline sub 63. When assembled, the two halves 61 and 62 of female spline sub 63 are brought together face-to-face to form said complete sub and so as to provide thereon a heavy cylindrical tubular body 64 which is machined internally to provide three female splines 65 and is turned down at its upper end to provide an annular, hammer 70 and male threads 71 (matching female threads 59) and a female taper 72 matching the male taper 60 on stabilizer sleeve 48. The opposite or lower end of the female spline sub body 64 is turned down to provide a lower annular hammer 73 which also receives an integral reinforcing ring 74 which is secured in place in uniting relation with the female spline sub halves 61 and 62 by cap screws 75, the heads of which are countersunk in said ring. The assembly of the female spline sub having been thus advanced by the application to the sub halves of integral reinforcing ring 74 as above described, the two halves as a unit are then screwed into the threads 59 provided in the lower end portion of stabilizer sleeve 48 so as to rigidly unite the two sub halves 61 and 62 are shown in FIG. 20. Further details relating to the mode of assembling female sub 63 will be made clear hereinafter.
The inner tubular element 27 of the tool comprises upper and intermediate thin walled sleeves 76 and 77 and a relatively heavy walledtubular male spline sub 78. The upper sleeve 76 makes a loose sliding fit upwardly within upper sub 28 when the tool 25 is in starting position as shown in FIGS. 1-5 inclusive and screws, at its lower end, into a threaded socket provided therefor and recessed in the inner face of the upper end of intermediate sleeve 77. The exterior face of sleeve 76 is concentrically spaced from the bore 31- 77 is an annular head 79 having external threads 80 on which is screwed the annular base of a mechanical tripping device 88 comprising a split tubular head divided into four inwardly yieldable quadrants 87, each bearing a quadrant shaped head 88 which normally underlies tripping ring 41 and has a matching face 89 which parallels the cani face 43 of ring 41 as clearly shown in FIG. 2. Each head 88 has at its upper extremity a guide wall 90 for guiding said head inside of the tripping ring 41.
A short distance downwardly from the lower end of tripping device base 85, the external annular head 79 of intermediate sleeve 77 is turned down to form a shoulder 91 and form a cylindrical surface on which an annular sleeve piston 92 may snugly fit. The external annular sleeve head 79 is also recessed to accommodate an O-ring 93 and is threaded to receive a nut 94 for tightly uniting piston 92 with annular head 79.
Beneath the external annular head 79 provided on the intermediate sleeve 77 of inner tubular element 27,
said sleeve is relatively thin walled so that its external surface 95 is spaced from counterbore 31 of outer tubular element 26 (see FIG. 3) so as to slidingly confine the packer 55 mounted upon the internal face of annular upper internal head 50 on stabilizer sleeve 48.
The annular sleeve piston 92 is also seen in FIG. 2 to make a close sliding fit with counterbore 40-of external tubular element 26 in this view which illustrates the invention in its starting position. Here, the piston 92 is disposed just above the cylinder 44 which is to stayout of conjunction therewith and entirely opposite the upper relief grooves 45 formed in counterbore 40 so as to allow a free passage of operating liquid vertically past piston 92 and past the cylinder 44 so long as piston 92 remains so positioned. 1
This piston is provided with a vertical hole which confines a gauge rod 101 for gauging the amount of free space in said hole left available for a flow of liquid therethrough and hole 100 is overlapped slightly at its ends by shoulder 91 and nut 94 so as to prevent the escape of rod 101 from said hole. Variations in the rate of travel of thecylinder 44 relative to the piston 92 during the operation of the jar 25 to effect an upward snap action jarring blow can be accomplished by selecting a pin 101, in assembling the tool before using the same, so as to accomplish the desired rate of travel of the piston 92 during the jarring operation. The external surface of the piston 92 is also provided with an annular groove for receiving an O-ring 102 which assures a tight sealing fit between the periphery of the piston 92 and the cylinder 94 when these two elements are in conjunction.
The lower end portion of intermediate sleeve 77 is externally threaded at 103 and provided with an external O-ring 104 to permit said sleeve to be screwed into and make a sealed connection with an externally enlarge'd upper annular head 105 provided on the upper end of male spline sub 78. This annular head makes a snug sliding fit with the smooth cylindrical bore 58 formed in stabilizer sleeve 48. These two elements are thus always in reinforcing relationship throughout the operation of the jar 25 which greatly adds to the effisplines 108.
The lower externally thickened annular head 106 of male spline 78 has provided thereon a threaded tool pin 109 for connecting the lower end of the jar to a drill collar 110 through which the jar 25 is connected to the fish, recovery of which is being sought.
Attention is now called to the fact that the provision of externally thickened annular heads 105 and 106 at the upper and lower ends of the male spline sub 78 provides on one integral element upper and lower anvil faces 115 and 116. This integration of these two faces in the male spline sub greatly strengthens the tool 25 in the vital shock area of the tool. The confining of the upper annular head 105 of the male spline 78 .within the stabilizer sleeve 48 so that this head is at all times in close sliding confinement by said sleeve, also powerfully reinforces said male spline sub in the area in which the maximum shocks are sustained by the tool.
The features just noted are made possible in the tool 25 by providing the female spline sub 63 in two halves 61 and 62 by splitting the femalesub lengthwise. It thus becomes unnecessary to make one end of the male spline sub of small enough diameter to permit the male spline sub to penetrate axially the bore of the female the pounding it must sustain by employing the upper and lower ends of the sub as hammer faces 70 and 73.
An added dividend derived from the design just described of the unit shown in FIG. 19, in which is concentrated the spline function as well as separate pairs of hammer and anvil faces for the performance of both up as well as down snap action jar operations, is the facility possessed by the jar 25 of permitting the replacesuch sub without the necessity of removing the jar from the string and in a relatively short shut down for this service.
OPERATION An annular chamber 117 is provided between the outer tubular element 26 and the inner tubular element 27 which is closed at its lower end by the fixed packer 55 and at its upper endby a sliding packer 32. One or more plugs 47 are provided for use in the conventional manner for filling chamber 117 with operating fluid,
which is generally a light lubricating oil, and for withdrawing the air from this chamber at the time the fluid is delivered thereto. When the tool 25 is in its normal starting position with the parts as shown in FIGS. l-5 inclusive, the entire chamber 117 is filled with operating liquid. As seen in FIG. 2, the cylinder 44 is out of conjunction at this time with the piston 92. Lifting the drill string 30 from this position to bring cylinder 44 v into conjunction with the piston 92 divides the hydraument of the female spline sub 63 in the jar by a new lie chamber 117 into a high pressure lower section and a low pressure upper section. The upper section always remains a low pressure area because of the freedom of the sliding packer 32 to shift vertically in response to any change in the relative pressures below and above said packer so that the pressure in the uppersection of the hydraulic chamber 1 17 is always substantially equal to the pressure of the ambient well fluid in which the tool 25 is operating. The inner tubular element 27 being connected through the drill collar 1 10 to the fish which is stuck in the well, elevation of the cylinder 44, bringing this into conjunction with the piston 92, is achieved by the driller raising the drill string 30 to tension the same.
With the parts of the tool 25 positioned as shown in FIGS. l-S inclusive, the driller has two options open to him in operating said tool. The first of these is to lifton the drill string 30 to bring the cylinder 44 into conjunction with the piston 92 which retards escape of the operating liquid in the high pressure section of the chamber 117, thus giving an opportunity to build up a relatively high tension strain on the drill string 30 during the travel of the cylinder 44 upwardly past the piston 92 and resulting in an upward snap action jarring operation when the hammer 70 strikes the anvil 115 as shown in FIG. 9.
The location of the respective elements of the jar 25 at the moment of delivery ofan upward snap action jarring blow by the tool 25 are illustrated in FIGS. 6-10 inclusive. Immediately following the delivery of this upward blow through the operation above described of the jar 25, the driller lowers the drill string 30 to return the parts of the jar 25 to their positions shown in FIGS. l-5 inclusive; This jar has the facility of providing a clear indication of the arrival of the parts of the jar in this position by the fact that as this position is reached, the tripping ring 41 comes to rest on top of the mechanical tripping device 86 by the sloping cam face 43 of said ring engaging the matching sloping faces 89 provided on the four inwardly yielding quadrants 87 of said device. These faces are cut approximately on a 20 angle with horizontal for the express purpose of requiring about 20,000 pounds of pressure on the device 86 before the latter will react by the quadrants 87 snapping inwardly to allow the ring 41 to pass downwardly around these quadrants into the position in which said ring is shown in FIG. 12. The reaction of the rig to the resistance to downward travel of the outer tubular element 28 provides a readily discernable signal to the driller at the top of the well indicating to him that the parts of the jar 25 are in the starting position shown in FIGS. l-5 inclusive. The driller is thus able to exercise without hesitation at this point the option as to whether he is going to continue lowering the drill string 30 beyond the starting position so as to effect a down snap.
of the type of jarring operation in each instance which he has programmed accomplishing with the jar 25.
Should the driller elect a repetition of the upward jarring operation, each of these operations would start therefore with the parts of the jar as shown in FIGS. 1-5 and constitute a repetition of the upward jarring operation just described. Whenever the driller elects to follow the arrival of the parts of the jar downward in their starting position as shown in FIGS. 1-5 inclusive, to accomplish a downward snap action jarringoperation, the driller merely continues his application of downward pressure to the drill string 30 on the outer tubular element 28 of the jar after the ring 41 is set down on the sloping faces 89 of the inwardly yieldable quadrants 87 of the tripping device 86. With the weight of the drill string 30 often being in the neighborhood of 100,000 pounds it takes only a short relaxation of the rig, while lowering the drill string 30, to apply 10 tons of pressure to the tripping device 86. When this pressure is reached however, a snap action downward jarring operation takes place in which the annular lower hammer face 73 of the female spline sub 63 is snapped downwardly from the position in which it is shown in FIG. 4 into violent impact with the annular hammer 116 as shown in FIG. 15.
It is to be noted that inthe starting position of the parts of the jar 25 shown in FIGS. 1-5 inclusive and particularly in FIG. 2, the cylinder 44 provided on the outer tubular element 26 has already' passed downwardly beneath the piston 92 so that there is no or very little resistance incurred in the passage of operating fluid past said piston and cylinder during the downward snap action jarring operation just described.- At the start of said operation, the piston 92 and cylinder 44 are relatively positioned 'as shown in FIG. 2 and at the conclusion of that jarring operation they are still further separated as shown in FIGS. 12 and 13. j
Following the operation of the jar 25 to effect a downward snap action jarring blow as shown in FIGS. 11-15 inclusive, the driller immediately operates his rig to lift the drill string 30 the short distance required to restore the parts of the jar to the position in which these are shown in FIGS. 1-5 inclusive. In this reaction of the parts of the jar to starting position, the driller is given a clear signal of the arrival of the parts of the jar at this position by the rapid increase in the strain imposedon continuing the lifting of said drill string, bythe annular cylinder 44 coming into conjunction with the piston 92 thereby greatly increasing the force required to continue lifting on the drill string. This constitutes a signal to the driller that the parts of the jar have reached their starting position shown in FIGS. 1-5 and, in case the driller wishes to exercise the option thus given him of repeating the downward snap action jarring blow just performed, he can readily do this by reversing his rig and starting to lower the drill string 30.
It is to be noted that when a downward jarring operation is performed with the jar 25, the ring 41, after being effective in springing the yielding quadrants 87 inwardly so that these no longer resist the downward movement of the outer tubular element 25, this ring slides downwardly past the quadrant shaped heads 88 and at the conclusion of delivery of the downward jarring blow being accomplished, the ring 41 has slid downwardly to a point where it is just above the annular base 85 of the tripping device 86. During the restoration of the parts of the jar 25 to their starting position, the upward movement of the outer tubular element 26 causes the ring 41 to slide up over and constrict the inwardly yielding quadrants 87. Upon ring 41 reaching its starting position shown in FIG. 12, said quadrant heads 88 will spring back outwardly under the ring 41 in readiness to initiate another downward snap action jarring operation.
The claims are:
1. In a duplex hydraulic-mechanical jar tool, the combination of:
inner and outer telescopically related tubular elements;
means for connecting one of said-elements to a drill string; I
means for connecting the other element to an object to be jarred, referred to herein as afish, telescopically overlapping portions of said elements providing an annular chamber for confining an operating liquid;
an annular packer supported on one element and slidably engaging the other element to close one end of said chamber;
an annular floating packer disposed between and slidably engaging both of said elements to close the other end of said chamber;
a relatively short piston extending radially outwardly from said inner element into said chamber;
a relatively short cylinder provided inwardly on said outer element in which cylinder said piston slidably fits to effect a dash pot retarding action on telescopic movement between said elements when said piston and cylinder are in conjunction; I
the'inner surface of said outer element being relieved in areas immediately above and below the zone of said cylinder, thereby releasing said elements from said dash pot retarding action when said piston and cylinder are out of conjunction;
said cylinder, when in conjunction with said piston, dividing said chamber into a low pressure section, adjacent to and containing said floating'pack'er and a high pressure section adjacent said first mentioned packer;
twopairs of impact shoulders provided on said elements which come respectively into axial abutting engagement when opposite ends of the entire range of relative telescopic movement between, said elements are reached,
said tool having an optional operation starting position wherein said cylinder has just passed out of conjunction with said piston and entered said high pressure chamber section; and
annular cam responsive spring resistance means provided on said elements in said low pressure chamber section and operative temporarily to halt further movement of said cylinder into said high pressure chamber section, until a predetermined heavy downward pressure has been applied through said drill string to said spring resistance means to cause the latter to suddenly release and thus produce a snap action downward jar operation,
an upward snap action jar operation being optionally automatically accomplished, starting with the tool in said starting position, by imposing and holding an upward strain of a predetermined value on said drill string.
2. A combination as recited in claim 1 wherein said piston makes a substantially liquid tight peripheral fit with said cylinder when said piston and cylinder are in conjunction,
said piston being provided with an axial hole allowing for the escape of operating liquid past said piston during the tensioning of said drill string;
a pin occupying said hole loosely to determine the rate of escape of said liquid, and
means for locking said pin in said hole yet readily permitting replacement of said pin with another differing in diameter to vary the rate of escape of said liquid.
3. A combination as recited in claim 1 wherein saidspring resistance means comprises:
a split tubular head co-axially spaced outwardly from said inner element and mounted at its lower end on said element, said head thus providing an annular series of circumferentially spaced radially flexible arms bearing at their upper ends outwardly, downwardly sloping cam faces, and
a ring means having an inwardlympwardly sloping cam face and fixed on said outer element to concentrically overly said cam faces of said arms and be closely juxtaposed therewith when said tool is in starting position.
4. A combination as recited in claim 3 wherein the angles of said cam faces on said head and said cam ring are approximately with horizontal.
5. A combination as recited in claim 1 wherein a lower end portion of said inner element comprises a male spline sub in which are integrally united a central male spline section and upper and lower annular head sections the external diameters of which head sections substantially exceed that of said male spline section;
said head sections having provided respectively thereon opposed upper and lower anvil impact faces; and wherein a lower end portion of said outer element comprises a longitudinally split female spline sub including two longitudinally separate halves which fit together on said male spline section to provide matching female splines;
ring means encircling said male spline sub and axially shiftable over the lower end of said assembled split female spline sub; and tapered pin thread means provided on an upper end portion of said female spline sub, there being matching threaded box means on the adjacent end portion of said outer element into which said tapered pin thread means screws to complete the assembly of said split female spline sub on said integral male spline sub.
6. In a duplex hydraulic-mechanical jar tool, the
inner and outer telescopically related tubular elements;
means for connecting one of said elements to a drill string;
means for connecting the other element to an object to be jarred, referred to herein as a fish;
longitudinallyspaced seal means forming a chamber between said elements for confining a body of operating liquid;
dash pot valve means temporarily restricting flow of said liquid lengthwise in said chamber under a heavy strain imposed on said drill string, then subsequently permitting said flow to produce an upward snap action jarring blow on said fish;
annular cam responsive spring resistance means provided on said elements and operative to temporarily halt telescopic contraction of said elements caused by lowering said drill string, following said blow, until sufficient pressure has built up to produce a downward snap action jarring blow; and
a spline unit at one end of said tool including an integral male spline sub having heavy external annular heads at its opposite ends, said sub comprising a portion of said inner tubular element,
a female spline sub, split lengthwise and assembled broadside on said male spline sub and united when so assembled with said outer tubular element; and
two pairs of movement limiting annular impact faces, one face of each pair being provided by an end of said female spline sub and the other face of said pair being provided by an end face of the annular male spline head located in juxtaposed relation with said first face of said pair.
7. In a deep well jar tool, the combination of:
inner and outer telescopically related tubular elements;
means for connecting one of said elements to a drill string;
means for connecting the other element to an object to be jarred, referred to herein as a fish;
means between said elements operating to restrain free telescopic movement between said elements in a given direction responsive to a strain imposed by said drill string for a relatively short distance and then permitting free movement between said elements;
an integral male spline sub having heavy external annular heads at its opposite ends, said sub comprising a portion of said inner tubular element;
a female spline sub, split lengthwise and assembled broadside on said male spline sub, an upper end portion of said female spline sub being provided with male pin threads;
a relatively thick walled stabilizer sleeve, comprising a lower portion of said outer tubular element, and provided, at its lower end, with female box threads matching said male pin threads, the latter being screwed into said threads of said stabilizer sleeve in assembling said female spline sub on said male spline sub,
the upper external annular head of said male spline sub making a sliding fit within said stabilizer sleeve thereby mutually reinforcing each other in all operating positions of the tool; and
means providing hammer and anvil impact faces on said spline stubs which are brought into collision, when said restraint is relaxed, to transmit a snap action jarring blow to said fish upon the termination of said telescopic relative movement between said tubular elements.