Well jar having a time delay section

A well jar has telescoping inner and outer elements having a torque transmitting connection therebetween. An intermediate member is rotatably mounted relative to the telescoping elements and is affixed in a longitudinal direction to one of the telescoping elements. A releasable latch is connected between the intermediate member and one of the telescoping elements. The intermediate member is rotatable relative to the telescoping elements upon a predetermined minimum longitudinal force applied between the telescoping elements. The rotation causes a release of the latch and movement of the telescoping elements to an impact of coacting impact faces on the telescoping elements. An improvement involves a time delay section connected between the intermediate member and at least one of the telescoping elements for restraining such relative rotation for a preselected time interval of application of at least such minimum longitudinal force. In addition the preferred embodiment has the time delay section and the latch located in a common chamber, and the time delay section includes a hydraulic time delay device that makes use of the same fluid as that used for lubricating the latch.

BACKGROUND OF THE INVENTION 
This invention relates to drilling tools and more particularly to a 
straight pull variable impact jarring mechanism for releasing objects 
stuck in a well bore. 
Well jars are known for imparting sharp jarring forces to an object stuck 
in a well bore. One prior art well jar has tubular shaped inner and outer 
telescoping elements. Inclined surfaces are affixed on the inner mandrel, 
and a roller, for each inclined surface, is mounted on the outer 
telescoping element. Each roller and corresponding inclined surface form a 
latch. An elongated open space extends in the inner element along the ends 
of the inclined surfaces into which the rollers move upon release of the 
latches. Coacting impact faces, one on each of the telescoping elements, 
impact at one extremity of longitudinal movement of the telescoping 
elements. One of the telescoping elements is for connection to the lower 
end of an upper drill string and the other telescoping element is for 
connection, for example, to an object stuck in a well bore. The latches 
hold the telescoping elements against relative longitudinal movement. In 
one mode of operation the latches are released by rotating the telescoping 
elements until the rollers and inclined surfaces of the latches are 
disengaged at which time the rollers enter the opening and the telescoping 
elements are allowed to freely move longitudinally relative to each other 
under an applied longitudinal force, causing the coacting impact faces to 
impact. Alternately, a torsion can be applied through the drill string to 
the corresponding telescoping element causing the inclined surfaces and 
rollers to be urged toward the latched position. A downward longitudinal 
force on the drill string of sufficient magnitude will cause an 
interaction of the rollers and inclined surfaces which rotates the 
telescoping elements against the applied torsion until the rollers reach 
the elongated opening, allowing the longitudinal force to drive the 
coacting impact surfaces into impact. Such an arrangement relies on 
torsion applied to the drill string to determine the magnitude of the 
longitudinal force required for a release of the latches. Additionally, 
the magnitude of the impact of the coacting faces depends on the magnitude 
of the torsion in the drill string. With such an arrangement, it is 
difficult to determine precisely the torsional forces on the jar, 
particularly when it is at the lower or end of a very long drill string. 
Additionally, momentary longitudinal forces on the jar, such as those 
caused by sudden braking of the drill string, may cause the jar to 
inadvertently release during a drilling operation. Additionally when 
rotating the drill string the inner and outer telescoping elements rotate 
relative to one another in one direction until the rollers engage the 
inclined surfaces and in the opposite direction until stops engage. 
An alternate prior art well jar also utilizes tubular shaped inner and 
outer telescoping elements with coacting impact faces. However, this 
device is provided with a tubular shaped intermediate sleeve member which 
carries inclined surfaces defining lateral notches. A longitudinally 
extending opening extends into the intermediate member along the ends of 
the notches. The inner telescoping element carries lugs which combine with 
the inclined surfaces to form latches. A spline connection is provided 
between the inner and outer telescoping elements to transmit torque 
directly from one to the other during a drilling operation. A torque 
spring is connected between the outer telescoping element and the 
intermediate member which rotates the intermediate member in a direction 
which engages the lugs in the notches. A longitudinal force applied in one 
direction between the telescoping elements will cause the adjacent 
surfaces of the notches and lugs to slide relative to each other, causing 
the intermediate member to be forced to rotate against the urging of the 
torsion spring. When the force on the intermediate member is of sufficient 
magnitude to overcome the torsion spring, the rotation is sufficient that 
the lugs enter the longitudinal opening at which point the telescoping 
elements freely move longitudinally relative to each other to one 
extremity where the coacting impact faces strike. With the splined 
connection between the inner and outer telescoping elements, a direct 
torque drive is provided between the telescoping elements during a 
drilling operation. However, momentary longitudinal forces applied between 
the telescoping elements of sufficient magnitude to overcome the torsion 
spring will cause the latches to release even though the user does not 
want the jar to release at that moment. 
A further alternate prior art well jar also has inner and outer tubular 
telescoping elements. An elongated opening and lateral V-shaped notches 
opening into the opening are provided in the inner telescoping element. 
Latches are formed by a V-shaped wedge for each notch, on the outer 
telescoping element. The notches and wedges of each latch have adjacent 
inclined surfaces which slide against the adjacent surface to cause a 
relative rotation of the telescoping elements. With the V-shaped notches 
and wedges, either tension or compression longitudinally between the 
telescoping elements will force the inner and outer telescoping elements 
to rotate relative to each other until the wedges enter the elongated 
opening and release, allowing the telescoping elements to move 
longitudinally until the coacting impact faces come together. A coupling 
on the inner telescoping element has a spline connection to the outer 
telescoping element for transmitting torque directly between the outer 
telescoping element and the coupling. The inner telescoping element is 
rotatable relative to the coupling, as well as the outer telescoping 
element, and a torsion spring is connected between the inner telescoping 
element and the coupling for urging the notch and wedges into engagement. 
Couplings for connection to an upper drill string and to a stuck object 
are provided on the coupling and outer telescoping element. Similar 
problems exist with respect to this device as mentioned with respect to 
the prior mentioned device. 
SUMMARY OF THE INVENTION 
A well jar embodying the present invention has telescoping inner mandrel 
and outer body elements. A connector is provided on each of the 
telescoping elements. An interconnection is provided between the 
telescoping elements for transmitting torque therebetween and is adapted 
to permit relative longitudinal movement therebetween. An intermediate 
element is rotatably mounted relative to and intermediate the telescoping 
elements and is affixed longitudinally relative to a first one of the 
telescoping elements. A releasable latch is connected between the 
telescoping elements. A releasable latch is connected between the 
intermediate element and one of the telescoping elements. The releasable 
latch prevents relative longitudinal movement of the intermediate and 
telescoping elements. Longitudinal relative movement between the 
telescoping elements causes the latch to impart relative rotation, between 
the intermediate element and such one telescoping element, to a release 
position wherein the releasable latch permits substantially free 
longitudinal movement between the telescoping elements. Time delay means 
is connected between the intermediate element and one of the telescoping 
elements for restraining the relative rotational movement to the release 
position for a preselected time interval of application of a longitudinal 
force between the telescoping elements. Coacting impact faces, one on each 
of the telescoping elements, are positioned for contact at an end of the 
longitudinal movement. 
With such an arrangement, longitudinal force between the telescoping 
elements is the sole external force which will cause the latch to release. 
Thus, torsional forces in the drilling string do not affect the amount of 
longitudinal force required to release the latch. Only the applied 
longitudinal force determines when a release occurs and determine the 
magnitude of the impact. Additionally, momentary oscillations such as 
tension or compression in a drill string connected to the jar, do not 
cause the jar to release even if the force required for triggering the jar 
is momentarily exceeded. Only if the force persists for the preselected 
time interval does the jar release. 
Preferably, a torsion spring is provided for urging the intermediate 
element with respect to the telescoping element away from the release 
position and predetermines a minimum amount of longitudinal force required 
to cause relative rotation, between the intermediate and the one 
telescoping element, to the release condition. 
A preferred embodiment of the invention has a time delay means with a 
converter for converting the rotational movement of the intermediate 
element into a linear longitudinal movement in the jar. A timer restrains 
the linear longitudinal movement for the preselected time interval. 
According to a further preferred embodiment, the time delay means is 
hydraulically controlled and includes a substantially fluid tight chamber 
extending longitudinally of the jar for containing a fluid. A piston is 
slidable longitudinally of the jar in the chamber and provides a 
substantially fluid isolated chamber portion on each end of the piston. A 
fluid flow regulator provides fluid flow by passing the piston from one 
chamber portion to the other to allow only a substantially constant flow 
of fluid, with variations in force on the piston. These and other 
preferred embodiments and features of the time delay mechanism disclosed 
in the present invention provide a construction of low maintenance and 
reliable operation. As a result the preselected time delay can be selected 
and remains constant over substantially the entire range of expected 
longitudinal forces. 
According to a further preferred embodiment the piston and the latch 
mentioned above are in a common chamber which has a common fluid for 
timing and for lubrication purposes. Preferably the timer is arranged 
downwardly from the latch so that air bubbles and light fractions of fluid 
will rise and not affect the the timer for operation of the piston. 
Preferably, a compensating seal is positioned at one end of the chamber to 
allow expansion of the chamber volume with expansion of the fluid in the 
chamber such as by changes of temperature of the fluid. 
According to a still further preferred embodiment, a constant fluid control 
piston part is provided for a well jar. The piston part has an elongated 
tubular shaped element having first and second ends and a diametrically 
enlarged and elongated circular central piston portion. A cam is provided 
at the first end and forms, when viewed from such end, at least a segment 
of a circle which is coaxial with respect to the piston portion and has, 
when viewed from a side, an inclined cam surface. At least one elongated 
finger member extends longitudinally from the second end of the piston 
part and forms, when viewed from such end, a segment of a circle which is 
coaxial with the piston portion. At least first and second passages extend 
between the ends of the central piston portion for a constant fluid flow 
regulator and a check valve.

DESCRIPTION OF THE INVENTION 
FIG. 1 is a side elevation view of a well jar 10 with a quarter section cut 
away to expose the internal parts thereof and which embodies the present 
invention. The well jar has telescoping inner tubular and outer tubular 
body elements 12 and 14, respectively. The elements 12 and 14 are made of 
metal strengthened by heat treatment or by other known techniques, as 
required to prevent wear and breakage. 
A female internal thread type connector 16 is provided at the upper exposed 
end of the inner element 12 for connection to the lower end of an upper 
drill string. A pin or male external thread type connector 18 is provided 
on the extreme opposite lower end of the outer element 14 for connection 
to the lower drill string or an object stuck in a well bore. The center of 
the inner element 12 allows circulation of drilling fluid, such as mud. 
An interconnection is provided between the telescoping elements 12 and 14 
for transmitting torque therebetween but allowing relative longitudinal 
movement between the telescoping elements. The connection is a spline 
connection 20 which includes inwardly longitudinally extending parrallel 
splines on the outer body element 14 and outwardly extending splines on 
the inner mandrel element 12 which allow relative longitudinal sliding 
movement. The spline connection 20 forms a portion of a torque drive 
section 22 allowing torque applied to the inner element 12 to be 
transmitted directly through the spline 20 to the outer element 14, 
bypassing the outer parts such as the latch. 
A latch mechanism or section 24 has an intermediate element in the form of 
a generally tubular shaped latch member 26 which is rotatably mounted 
relative to and intermediate the inner and outer telescoping elements 12 
and 14. The intermediate latch member 26 is separated in a longitudinal 
direction from the outer element 14 by anti-friction thrust bearings 28. 
Two ring springs 29 and 30 prevent longitudinal movement of the 
intermediate member 26 relative to the outer telescoping element 14 while 
allowing relative rotation therebetween. To be explained in more detail, 
the intermediate member 26 has upper and lower parts 26a and 26b 
interconnected by a finger spline 51. Also the upper part 26a is connected 
to a torsion spring 48 by a finger spline 49. The ring springs 29 and 30 
load the upper and lower parts 26a and 26b to the left as seen in FIG. 1 
so as to maintain contact with thrust bearings 28. Bushings 32 rotatably 
mount the intermediate member 26 on the interior wall of the tubular 
shaped outer element 14. 
The latch section 24 includes a plurality of latches 34. Each latch 34 
includes a first part in the form of a roller 36 whose axis extends along 
a radius towards the center line of the well jar. Each roller is rotatably 
mounted on a bearing spindle 37 which is affixed to the intermediate latch 
member. The bearing is positioned in a circular recess from the exterior 
of the tubular shaped intermediate latch member 26. 
Each latch includes a second part on the inner element 12 in the form of a 
cam 38. The cam 38 is engageable with the roller 36 when latched so as to 
prevent relative longitudinal movement of the intermediate latch member 26 
with respect to the inner element 12 and as a result prevents relative 
longitudinal movement of the telescoping elements 12 and 14. To be 
explained in more detail, relative rotation of the intermediate latch 
member 26 and the inner element 12 to a breakaway position of the latch 
allows the roller 36 to move into a longitudinally elongated opening 39 in 
the inner element 12, allowing the roller 36 (and hence the intermediate 
latch member 26) to move longitudinally relative to the inner element 12. 
Also to be explained in more detail, the cam 38 has an inclined cam 
surface which, upon application of longitudinal force either in 
compression or in tension between the inner and outer telescoping elements 
12 and 14, causes the intermediate latch member 26 to rotate relative to 
the inner telescoping element 12 to the breakaway position of such latch 
parts. 
Significant to the present invention there is provided a time delay means 
in the form of a timer section 40. The timer section is connected between 
the intermediate latch member 26 and the outer element 14 and restrains 
relative rotational movement of the intermediate latch member 26 to the 
breakaway position for the latches for a preselected time interval of 
application of longitudinal compression or tension forces between the 
inner and outer telescoping elements 12 and 14. Details of the timer 
section will be described in connection with FIG. 2. 
A hammer section 42 has coacting impact faces 44 which strike or impact 
upon application of tension forces between the inner and outer telescoping 
elements 12 and 14. Impact faces 46 impact under compression applied 
between the telescoping elements 12 and 14. 
Resilient means in the form of the torsion spring 48 is provided in a 
torsion spring section 50. The torsion spring 48 is connected by an 
involute spline 52 on a collar 54 to a spline on an annular extension 56 
on the outer element 14. The other end of the torsion spring 48 is affixed 
radially through the semicircular finger spline connection 49 to one end 
of the intermediate latch member 26. The torsion spring 48 is preloaded 
about the longitudinal axis of the jar between the outer element 14 and 
the intermediate latch member 26 so as to rotate the intermediate latch 
member relative to the inner element 12 until the rollers 36 are bottomed 
in the cams 38. As will become evident during the following discussion, 
relative rotation to the engaged position of the latch 34 can only occur 
when the inner and outer telescoping elements 12 and 14 are longitudinally 
moved to the position where the roller 36 and cam 38 of all latches 34 are 
longitudinally aligned. 
Consider now in more detail the arrangement of the latches 34. The latches 
34 are arranged into groups 57. Four groups of latches 57 are positioned 
in a straight line extending longitudinally along the inner element 12 and 
the intermediate latch element 26. Each group has four latches 34 and each 
group is separated longitudinally with respect to the adjacent group. FIG. 
3 is an enlarged view of the inner mandrel 12 in the circled area 
indicated in FIG. 1. FIG. 4 is a cross-sectional view of the inner mandrel 
12 taken along line 4--4 of FIG. 3. In addition to the four longitudinal 
groups seen in FIG. 1, for each group seen in FIG. 1 there are two 
additional groups of latches 57 angularly spaced at 120.degree. increments 
around the inner mandrel 12. The three angularly displaced lines of 
latches 34 are generally indicated by the three angularly displaced cams 
38 and openings 39 depicted in the cross-sectional view of the inner 
element 12 shown in FIG. 4. 
As described above, each latch 34 contains a roller 36 mounted on the 
intermediate member 26 and a cam 38 in the inner mandrel 12. Referring to 
FIGS. 3 and 4, each cam 38, as best depicted in FIG. 3, has two facing but 
diverging inclined surfaces 58 and 60 which diverge outwardly from a 
bottom 62 of the cam towards the elongated opening 39. The surfaces 58 and 
60 are inclined and diverge helically with respect to a center line 64 
which is a tangent to the inner element 12 and is also perpendicular to 
the central axis of the inner element 12. As depicted in FIGS. 1, 3 and 4, 
longitudinally elongated opening 39 is provided along each line of 
latches. The elongated opening 39 extends in a straight line along the 
inner element 12 in communication with the openings of each of the cams 38 
disposed along the same longitudinal line. 
Thus the torsion spring 48 urges the intermediate latch member 26 relative 
to the inner element 12 so that the rollers 36 engage the bottom 62 of the 
corresponding cam. 
Consider briefly the operation assuming that there is no effect due to the 
time delay section 40. When a longitudinal compressive force is applied 
between the inner and outer telescoping elements 12 and 14, such as occurs 
when the outer element 14 is fixed and a downward force is applied to the 
upper drill string connected at 16, each roller 36 will roll on the 
corresponding inclined surfaces 60, forcing the intermediate latch member 
26 to rotate in a clockwise direction as viewed from the connector 16 end 
of the jar. Rotation continues until the roller 36 reaches a release or 
breakaway position where it is in the corresponding elongated opening 39 
whereupon the inner element 12 drops downward free of the holding action 
of the rollers 36. The downward movement of the inner element 12 continues 
until the coacting impact faces 46 strike, imparting a sharp downward 
impact force to a stuck object connected to the connector 18. A similar 
action occurs when tension is applied between the elements 12 and 14 such 
as occurs when the outer element 14 is fixed and the inner element 12 is 
pulled upward. Tension will cause each roller 36 to bear against the lower 
surface 58 of the corresponding cam 38 forcing the intermediate latch 
member 26 to rotate clockwise, viewed from connector 16, until the rollers 
reach the unlatched or breakaway position and enter the corresponding 
elongated opening 39. When this occurs the inner element 12 moves upwardly 
with respect to the intermediate latch member 26 and the outer element 14 
with the rollers traveling in the corresponding opening 39 until the 
coacting impact faces 44 strike, imparting a sharp upward blow to a stuck 
object connected to the lower connector 18. 
It will now be seen that the torsion spring 48 applies a torque which 
restrains the rotation of the intermediate latch member 26 relative to the 
inner and outer telescoping elements 12 and 14 until a minimum amount of 
longitudinal force is applied between the telescoping elements. By 
increasing the spring preload the amount of force required to rotate the 
intermediate latch member 26 to the breakaway position of the latches 34 
is increased. 
Refer now to the timer section 40 as best seen in FIG. 2. The timer means 
or section 40 is connected between the intermediate latch member 26 and 
the outer element 14 for restraining the relative rotational movement of 
the intermediate latch member 26 so that the breakaway position of the 
latch is not reached for a preselected time interval. The time interval is 
measured beginning with the time at which sufficient longitudinal force is 
applied between the telescoping elements to overcome the counteracting 
preload of the spring 48. Included therein is a converter 65 for 
converting the rotational movement of the intermediate latch member 26 
into a linear longitudinal movement in the jar. The converter 65 includes 
a first part 66 on the intermediate latch member 26 and a second part 68 
on a tubular part 73. The parts 66 and 68 have facing inclined cam 
surfaces 66a and 68a, respectively, best seen in FIGS. 2, 5 and 7, which 
slidably engage each other. With this arrangement, rotation of the 
intermediate latch member 26 causes rotation of part 66 which in turn 
causes the surfaces 66a and 66b to rotate relative to each other. The part 
68 is fixed so it cannot rotate and hence rotation of the surfaces 66a and 
68b causes a force against inclined surfaces 68a and 68b causing a 
longitudinal movement of the part 68 to the right as viewed in FIGS. 2 and 
7. In this connection it should be noted that the intermediate latch 
member 26 will always move in the clockwise direction as viewed from the 
connector 16 end of the jar. 
Timer section 40 has a substantially fluid-tight circular annular shaped 
chamber 72 which extends longitudinally in the jar for containing a fluid 
such as oil. The tubular part 73 includes a diametrically enlarged 
centrally located piston 74 which is elongated in a longitudinal direction 
in the jar and slidable in a longitudinal direction within the chamber. 
The piston 74 provides a substantially fluid-isolated chamber portion on 
each end thereof. The piston 74, similar to the intermediate latch member 
26, is tubular shaped so that it slides along between the outer surface of 
the inner element 12 and the inside surface of the outer element 14. 
At one angular position of the piston 74 there is provided a regulator 76. 
The regulator 76 is a constant fluid flow type regulator that only allows 
a substantially constant rate of flow of fluid through the piston 74 from 
end 74a to end 74b over the expected variations in force created by the 
rotational to linear converter 65 under longitudinal force between the 
telescoping elements 12 and 14. The regulator 76 is positioned in a 
passage 75 which extends between the ends 74a and 74b. 
In addition to the regulator 76, which provides a substantially constant 
fluid flow from end 74a to end 74b, a check valve 78 is provided. The 
check valve 78 is located in a passage 80 extending between the ends 74a 
and 74b of the piston 74. The check valve 78 blocks the flow of fluid from 
end 74a to end 74b but allows fluid to freely flow from end 74b to 74a. 
There is one additional constant flow regulator 76 in a separate angularly 
displaced passage 75 (not shown) identical to the one discussed above. 
Also there are 13 additional check valves 78 separately positioned in 14 
additional angularly displaced passages 80 (not shown), identical to the 
one described above. The passage 75 (and the respective flow regulators 
76) and the passages 80 (and the respective check valves 78) are all 
connected in between the ends 74a and 74b of the piston in the same 
direction as the one described. The invention is not limited to any 
specific number of passages and regulators and check valves, the 
aforementioned being given by way of example. Although not essential to 
the invention, 16 passages are positioned at equal angular positions and 
extend in between ends 74a and 74b, two of which are used as passage 75 
(with regulators 76) and fourteen of which are used as passages 80 (with 
check valves 78). In one embodiment it has been found desirable to 
position the regulators 76 in the passages 75 adjacent the end 74b rather 
than the end 74a and place a screen over the passage at the end 74a in 
order to prevent foreign particles in the fluid from altering the time 
delay of the regulators. 
The regulators 76 are type 281 Flosert, made by the Lee Company. A screen 
(not shown) covers the end of the regulator 76 facing to the right to 
prevent particles from entering the regulator. The check valves are size 
187 made by the Lee Company. However, these devices are given by way of 
example and the invention is not limited thereto. 
The ends of the piston 74 are sealed between the outer wall of the piston 
74 and the inner wall of the outer body element 14 by o-ring 81 positioned 
partially in an annular groove around the periphery of the piston 74. The 
ends of the piston 74 are sealed in between the inner wall of the piston 
74 and the outer wall of the inner element 12 by an o-ring 82 partially in 
an annular groove around the inner periphery of the piston 74. 
In operation, when longitudinal force is applied between the telescoping 
elements 12 and 14 of sufficient magnitude to overcome the restraining 
force of the torsion spring 48, the intermediate member 26 starts to 
rotate relative to the inner and outer telescoping elements 12 and 14 
towards the breakaway position of latches 34. However, the tendency to 
rotate is converted to a linear motion by the converter 65 thereby 
applying a force to the piston 74 tending to move it to the right hand end 
of chamber 72 as seen in FIG. 2. As a result, pressure builds up on the 
end 74a of the piston 74. Such flow of fluid is blocked by the check valve 
78 but is permitted to flow by the regulator 76 through the passage 75 to 
the end 74b. The regulator 76 being a constant flow type regulator, allows 
a metered amount of flow to occur. After sufficient fluid has passed 
through the regulator to the end 74b of the piston to allow the piston 74 
to move longitudinally to the point where the intermediate member 26 may 
rotate to the breakaway position of the latches, then the longitudinal 
movement of the telescoping elements 12 and 14 and the hammer action 
discussed above occur. 
A spiral compression spring 83 is positioned in the chamber 72 and bears 
against the end 74a of the piston 74. The jar is reset after release of 
the latches by relatively moving telescoping elements 12 and 14 until the 
rollers line up with and rotate into engagement with the the corresponding 
cams under the force of the spring 48. After this occurs the pressure 
between the parts 66 and 68 is relieved, allowing the spiral spring 83 to 
force the piston 74 to the left to its initial position where the end 74b 
abuts against the inwardly extending shoulder 14a of the outer body 
element 14. 
The jar contains a static timer seal cartridge 85. The seal cartridge 85 
contains a male involute spline 84 which engages with a female spline 
formed on the interior of the outer body element 14. The engaging splines 
84 and 86 prevent the static timer seal cartridge 85 from rotating and in 
turn prevent the piston 74 from rotating under force created by the 
latches. As best seen in FIGS. 2 and 9, the static timer seal cartridge 85 
contains three longitudinally extending finger members 88 (only two being 
shown in the Figures). The fingers 88 form segments of a circle and are 
spaced apart by equal angles. The end 74a of the piston 74 has three 
axially extending fingers 90 which also form segments of a circle and 
extend in an axial direction and in between the sides 88a of the fingers 
88 so as to form a finger spline connection. The sides 88a and 90a of the 
fingers 88 and 90, respectively, engage and, due to the rigid spline 
connection of the static timer seal cartridge 85, prevent the piston 74 
from rotating while allowing sliding longitudinal movement of the surfaces 
88a and 90a of fingers 88 and 90 as the piston 74 moves in a longitudinal 
direction. The opposite end of the spiral spring 83 from the piston 74a 
bears against the longitudinal facing surface of the static timer seal 
cartridge 85. An extension sub 92 carries the connector 18 at the lower 
end of the jar and at the opposite end of extension sub 92 a threaded male 
connector is provided for mating with a threaded female connector provided 
on the interior wall of the outer element 14. The extension sub 92 forms a 
plug which engages the lower end of the static timer seal cartridge 85 and 
prevents it from moving axially out of the lower end of the jar. 
Significantly, the fluid chamber 72 is elongated and extends in between the 
inner and outer telescoping elements 12 and 14 from the static timer seal 
cartridge 85 to a compensating seal section 93 and hence includes both the 
timer section 40 and the latch section 24. As a result the same fluid 
which is used for controlling the timer section 40 is used for lubrication 
purposes in the latch section 24. Further, the latch section is 
positioned towards the splined connection 20 from the timer section 40 and 
is therefore positioned upwardly in the normally intended vertical 
position of the jar. As a result, lighter fractions of fluid created by 
bubbles, impurities, etc., in the fluid will tend to rise in the chamber 
72 away from the piston 74 thereby providing a more reliable, constant 
delay period. 
The compensating seal section 93 provides an expandable volume for the 
chamber 72. The compensating seal section 93 includes a tubular shaped 
seal 94 positioned between the inner and outer telescoping elements 12 and 
14. Outer o-rings 96 are provided in annular grooves around the outer 
surface of the seal member 94 in order to provide a fluid-tight seal 
between the member 94 and the inner surface of the outer element 14. 
Similarly, o-rings 98 are provided in recesses in the inner surface of the 
member 94 so as to provide a fluid-tight seal between the member 94 and 
the inner element 12. With such an arrangement the member 94 is able to 
slide longitudinally between the inner and outer telescoping elements 12 
and 14 and yet provide a fluid-tight seal for the chamber 72. A spiral 
compression spring 100 is positioned in an annular space around the inner 
element 12 and is disposed in a longitudinal direction in the jar between 
an end of the member 94 and an inwardly extending shoulder 102 of the 
outer element 14. The spring 100 urges the compensating seal member 94 
towards an inwardly extending shoulder 104 of the outer body element 14. 
As the fluid in the chamber 72 expands, the seal member 94 will be forced 
towards the inwardly extending shoulder 102 thereby expanding the volume 
within the chamber 72. As the fluid volume decreases, the member 94 will 
move towards the shoulder 104 due to the force of the compression spring 
100. 
In order to facilitate the longitudinal sliding relative movement of the 
inner and outer telescoping elements 12 and 14, four annular bushings 106 
are affixed to the outer element 14 and between the inner and outer 
telescoping elements 12 and 14 at longitudinally spaced apart positions 
for providing a sliding bearing between the elements. 
Openings 108 in the torque drive section 22, openings 110 in the hammer 
section 42, and openings 112 in the compensating seal section 93, allow 
mud to circulate into the corresponding sections of the jar. 
Although o-rings have been disclosed as seals herein it will be understood 
that other types of seals can be used as will be evident to those skilled 
in the art and are contemplated within the scope of the invention herein. 
To facilitate the assembly of the jar, the outer body element 14 is 
arranged into separate outer body parts 120 through 126. Each outer body 
part has a threaded connection to an overlapping portion of the adjacent 
outer body part. Also the inner telescoping element 12 has an upper part 
12a and a lower part 12b connected together by a threaded connector 130 
which carries one of the impact faces 44. 
Prior to the major assembly, the bushings 106 for the inner telescoping 
element 12 are mounted using the retaining rings 107. The tool joint seals 
109 are inserted in the outer body connections. The seals 81, 82, 96, 98 
and 111 are mounted in the seal cartridge assembly 85, the piston 84 and 
the seal member 94. The regulators 76 (and a screen for each regulator) 
and the check valves 78 are affixed in the piston 74 as described above. 
The actual assembly of the well jar moving from left to right is as 
follows: 
The outer body part 120 is slid onto the upper part 12a of the inner 
telescoping element 12, forming the spline connection 20. The connector 
130 is threaded onto the upper part 12a and is affixed thereto with 
screws. The following elements are then placed on the lower part 12b of 
the inner telescoping element 12: outer body part 122, the seal member 94, 
the seal spring 100, the outer body part 121. The lower part 12b of the 
inner telescoping element 12 is then threaded into the remaining end of 
the connector 130 and affixed thereto by screws. The outer body parts 120, 
121 and 122 are then threaded together. 
The torsion spring 48 is positioned over the lower end 12b of the inner 
telescoping element 12 and the splines 56 thereof are engaged with the 
splines 52 on the outer body part 122. The outer body part 123 is 
positioned over the lower part 12b of the inner telescoping element 12 and 
threaded with the outer body part 122. The thrust bearing 28 is positioned 
over the front end of the upper part 26a of the intermediate member 26. 
The upper part 26a of the intermediate member 26 is positioned over the 
lower part 12b of the inner telescoping element 12 and the finger splines 
49 are engaged at the lower end of the torsion spring 48. 
The torsion spring 48 is then preloaded by twisting the front 26a of the 
intermediate member 26 counterclockwise, as viewed from the right hand end 
of FIG. 1, until the openings for the rollers in the upper part 26a of the 
intermediate member 26 line up with the corresponding openings 38 in the 
inner telescoping element 12. The rollers 36 are then positioned into the 
upper part 26a of the intermediate latch member 26, maintaining the 
preload for the spring 48. The split bushings 32 are positioned on the 
upper part 26a of the intermediate latch member 26 and the thrust bearing 
assembly 28 and the ring spring 29 are positioned at the lower end of the 
upper part 26a of the intermediate latch member 26. The outer body part 
124 is slid over the upper part 26a of the intermediate element 26 and 
threaded together with the lower end of the outer body part 123. 
The assembly is then unlatched and impact faces 46 touch. The thrust 
bearing 28 is then positioned over the upper end of the lower part 26b of 
the intermediate latch member 26. The lower part 26b of the intermediate 
latch member 26 is then slid over the lower part 12b of the inner 
telescoping element 12. The rollers are then positioned into the openings 
provided in the lower part 26b of the intermediate latch member 26. The 
lower part 26b is progressively pushed to the left as seen in FIG. 1 as 
the rollers are inserted in place until the finger spline 51 is fully 
engaged. The thrust bearing 28 and split ring spring 30 are positioned at 
the lower end of the lower part 26b. The outer body part 125 is then 
threaded into the outer body part 124. 
The jar is subsequently latched and the tubular part 73 (carrying piston 
74) is positioned over the lower part 12b of the inner telescoping element 
12, fully engaging camming surfaces 66 and 68. The spiral compression 
spring 83 is then positioned about the tubular part 73 and the static 
timer seal cartridge 85 is positioned about the lower part 12b, 
compressing the spiral compression spring 83 until the finger splines 88 
and 90 are fully engaged. 
A slot 132 is provided at the right hand end of the static timer seal 
cartridge 85 in alignment with an opening 131 in the outer body part 125. 
A retaining pin 128 is positioned through the opening 131 into the slot 
132 thereby holding the cartridge 85 with the spring 83 preloaded. 
Although the slot 132 is shown by way of example, it should be understood 
that an annular groove may be provided in the static timer seal cartridge 
for the pin 128 by appropriately extending the static timer seal cartridge 
to the right (as seen in FIG. 2) past the filler plug 134. 
Two-way vacuum filler plugs 134 and 138, having threads on the exterior 
thereof, are respectively threaded into the static timer seal cartridge 85 
and the end of the outer body part 122 which is adjacent to the outer body 
part 123. The two-way vacuum filler plug 134 communicates with one end of 
the chamber 72 via the passage 136. The two-way vacuum filler plug 138 
communicates with the other end of the chamber 72 through an opening in 
the outer body part 122 and a relief in the adjacent annular bushing 106. 
It will be noted at this point that the outer body part 126 which is a 
part of the extension sub 92 has not been positioned in place, leaving the 
filler plug 134 (in the static timer seal cartridge 85) exposed. 
FIG. 11 shows an enlarged cross-sectional view of the bushing 106 which is 
positioned under the two-way filler plug 138 at 1A of FIG. 1. FIG. 12 
shows an end view of the same bushing. As indicated, the bushing shown in 
FIGS. 11 and 12 contains two annular grooves extending around the 
circumference of the bushing, and four longitudinal grooves, the latter 
spaced 90.degree. apart. Depending on the direction in which the bushing 
106 is inserted, one of the annular grooves is aligned with the two-way 
filler plug 138 thereby allowing fluid to freely flow into the annular 
groove through the longitudinal groove to opposite ends of the bushing. 
Additionally the longitudinal grooves allow fluid to move within the 
chamber 72 from one end of the bushing to the other. 
The method and procedure for filling the well jar so as to completely fill 
the hydraulic timer section 40 and the latch mechanism chamber are quite 
important. In this connection it will be noted that the chamber 72 is 
separated into one chamber part at the right of piston 74 and a second 
chamber part at the left of piston 74. The regulators 76 and the check 
valves 78 provide a restricted flow for fluid between the ends of piston 
74. Additionally the regulators and check valves have a minimum cracking 
pressure at which fluid will flow therethrough. Accordingly, care must be 
taken to ensure complete and uniform filling of the fluid into both 
chamber parts. 
Referring to FIG. 10, a source of vacuum 150 is connected through a shutoff 
valve 152 to a tee fitting 154. Similarly, a reservoir 156 of fluid, of 
the type desired in chamber 72, is connected through another shutoff valve 
158 to another side of the tee fitting 154. The remaining leg of the tee 
fitting 154 is connected through a second tee fitting 160 to the filler 
plugs 134 and 138. 
The filler plugs 134 and 138 are rotated to a fill position leaving the 
lower o-ring of each plug out of the small hole of the corresponding 
opening so that a clear passage exists through both of plugs 134 and 138 
into opposite ends of the chamber 72. Valves 152 and 158 are turned off so 
as to block the filler plugs from both of the sources 150 and 156. 
Subsequently the shutoff valve 152 is opened, applying vacuum through tees 
154 and 160 to the filler plugs 134 and 138, causing the chamber 72 to be 
evacuated. Also the vacuum is left on long enough to not only create a 
vacuum but to draw out undesirable fluids remaining in the chamber 72. 
With the vacuum maintained in the chamber 72, the shutoff valve 152 is 
turned off and the valve 158 is turned on, allowing fluid in the reservoir 
156 to flow through the tees 154 and 160 through the filler plugs 134 and 
138 and into the chamber 72 until the fluid completely fills the chamber 
72 from opposite directions. 
By this method it is possible to completely fill the chamber 72 with its 
many parts, shapes and angles with the restriction of the regulators and 
check valves, without leaving air bubbles. This is quite important since 
it is necessary to have a uniform fluid and a uniform fluid pressure for 
proper operation of the piston 74. 
With the fluid reservoir connected to the ports, the filler plugs 134 and 
138 are tightened down until the lower o-rings thereon are tightly fitted 
against the walls of the smaller diameter of the respective ports, thereby 
sealing the ports. The vacuum pump and fluid fill lines are then removed. 
The outer body part 126 forming the extension sub 92 is then threaded into 
place on the right hand end of the outer body part 125 and the retaining 
pin 128 is removed. The extension sub thereby forms a retainer to hold the 
seal cartridge in place. 
Although an examplary embodiment of the invention has been disclosed for 
purposes of illustration, it will be understood that various changes, 
modifications and substitutions may be incorporated into such embodiment 
without departing from the spirit of the invention as defined by the 
claims appearing hereinafter.