Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention concerns hydraulic jars for deep well
drilling which can be installed as a component in a drill pipe
string, with an outer pipe body and an inner pipe body
defining with the latter an annular space filled with a
pressure medium, where the outer pipe body and the inner pipe
body are displaceable coaxially relative to each other and are
provided with an inner percussion piston acting as a hammer
adapted to strike an anvil, when the inner and outer pipe
bodies move apart, as well as with end stops for limiting
telescopic movement between the inner and outer pipe bodies.
Hydraulic jars of this type are used in deep well
drilling as a part of the drilling string, so that the drilling
string can be loosened quickly by upwardly or downwardly
directed hammer blows when it gets stuck in the borehole.
Upwardly directed blows, and also downwardly directed blows,
depending on the design of the jars, are produced by a
separating movement of inner and outer pipe bodies caused by
axial tensile forces introduced into the drilling string, by
means of the percussion piston acting as a hammer. As a
result of the telescopic movement of the inner and outer pipe
bodies, downwardly directed blows, which are produced by
limited raising and then lowering of the drill string, can be
performed by the jars on the part of the drilling string
arranged below the jars. Such hydraulic jars are character-
ized by a great force of the hammer blow, which is regulatable
within wide limits, and which can be adjusted or varied in a
simple manner by the operator at the drilling installation
above the borehole at any time during the drilling operation,
while the jars are in the borehole.
In mechanical jars, on the other hand, the force of the
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blow must be preset at the drilling installation and can nolonger be varied during the operation of the jars in the
borehole. Due to the presetting of the load, which causes
the upwardly and downwardly directed blows of the mechanical
jars, the latter can only be installed in the drilling string
at those points where it is substantially free of axial
pressures. It is, therefore, limited to installation in the
upper end region of the drill stem assembly,for example,
directly above the top stabilizer in the drill string, since
there is a great risk of accidental release of the jars for a
blow, due to the high axial pressure acting on the upper part
of the jars, which could result in damage to the drilling bit
or other tools in the drill string. On the other hand,
however, the preset force of the jars with the usual arrange-
ment in the upper part of the drill stem assembly, is notsufficient in many cases to loosen the drill string when it
gets stuck inside the stabilized region of the drill stem
assembly. Mechanical jars installed in the upper region of
the drill stem assembly, or in the adjoining transition
linkage, therefore, can do their job only as a rule if the
drill string gets stuck above the stabilized region of the
drill stem assembly.
A desirable arrangement of hydraulic jars of the above
indicated type, in a range above the drill stem assembly or
at a considerable distance above the stabilized region of the
drill stem assembly, still involves considerable risks which
are caused by the design of the hydraulic jars. When the
drill string is lowered into the borehole with such an
arrangement of the jars, the great weight of the part of the
0 drill string below the jars causes a relatively rapid
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separating movement of the inner and outer pipe body of the
jars, at the end of which is imposed a vigorous upwardly
directed blow. Such a blow represents a hazard for the
operating personnel at the drilling installation, particularly
when they are not prepared for such a blow. This is very
frequently the case, since the jars which are extended during
the separating movement of the inner and outer pipe bodies is
telescoped when the drilling string is lowered into the
borehole, either striking the lower part of the drilling
string accidentally on projecting edges or shoulders in the
borehole, or by the resistance of liquid contained in the
borehole, and exerts a blow subsequently. Such accidental
blows represent a particular hazard if the drilling string is
caught at the drilling installation in the slips of the
rotary table, which can be shifted by such blows out of their
holding engagement with the drilling string, and can lead to
loss of the entire drilling string when it drops into the
borehole. For this reason, hydraulic jars can be used, as a
rule, only in the lower part of the drill stem or string
assembly, that is, directly above the top stabilizer, an
arrangement where the above-mentioned accidental blows do not
have the above described far-reaching and dangerous effects,
but where the assembly can be jarred loose effectively.
The invention is based on the problem of providing jars
of the above-described type which can be installed at any
point in the drilling string and is secured against accidental
blows until it is brought at a selected time into a state
where it is conditioned for imparting a hammer blow.
This problem is solved according to the invention in a
manner that the inner pipe body and the outer pipe body are
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locked, at least in a partly telescoped position, by a locking
device against further axial relative separating movement,
the locking device being releasable by s~lbjecting the jars to
a predetermined axial pull acting between the inner and the
outer pipe bodies.
Due to this design, the delivery of jarring blows by
the inner and outer pipe bodies moving apart by the necessary
amount is positively avoided, until the jars are subjected
deliberately by the operating personnel of the drilling
installation with a predetermined axial pull, namely, a
certain overload, which acts between the inner and outer pipe
bodies and thus releases or unlocks the locking device. This
is, as a rule, only necessary when the drilling string gets
stuck, which happens generally only after it has fully entered
the borehole. As long as the drilling string hangs in the
slips of the rotary table of the drilling installation or
during its lowering into the borehole, accidental blows are
positively prevented from occuring. This provides the
possibility of installing jars according to the invention in
the drilling string not only in the stabilized region of the
drill stem assembly, e.g. directly above the top stabilizer,
but at any desired point, for example, in the upper region of
the drill stem assembly, or considerably above it. It is,
thus, no longer necessary to keep different types of jars in
stock, for example, mechanical and hydraulic jars, for
different purposes or at different points in the drilling
string. During lowering of the drilling string, the locked
jars can transmit downwardly directed shocks or blows of the
drilling shaft to overcome obstacles, or act as a buffer gear,
that is, as a so-called bumper sub, while it performs all
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functions of ordinary hydraulic hammer jars without limita-
tions in its operating state.
In another development of the invention, the locking
device can be formed by one or several parallel safety members
connecting the inner pipe body with the outer pipe body, which
provide a simple arrangement of locking the inner and outer
pipe bodies.
Preferably, however, an additional closed annular space
filled with a pressure medium is provided in the upper or
lower region of the jars between the inner and the outer pipe
bodies, acting as a hydraulic locking device, which is closed
at one end by an annular piston, bearing on the inner or outer
pipe body at its end face remote from the interior of the
annular space, being connected with the surrounding outer pipe
body and having at least one pressure relief valve which opens
when the pressure medium enclosed in the annular space attains
a predetermined overpressure.
This hydraulic locking device permits a partial
separating movement of the inner and outer pipe bodies by
partially filling the additional annular space with the
pressure medium, e.g. up to half the total extension path of
the jars, which now permits, by the telescopic movement of the
inner and outer pipe bodies, stronger downward blows when the
drilling string is lowered into the borehole. In the event
the part of the drilling shaft below the jars encounters
resistance in the borehole only when the drilling string has
been completely lowered into the borehole, and it is
necessary to perform upward blows by means of the hydraulic
jars during the drilling operation when the drilling string
gets stuck, the inner and outer pipe bodies of the jars are
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extended by applying the predetermined axial pull or overload
from the drilling installation at the surface of the well by
opening the pressure relief valve, which produces an upward
blow by means of the percussion piston or hammer striking the
opposite shoulder or anvil.
Other features and advantages of the invention will
result from the following description in connection with the
drawing, in which several embodiments of the subject of the
invention are illustrated.
Figure 1 shows four views, Figs. la, lb, lc, ld, of
partial regions of differently composed drilling strings with
installed hammer jars in a schematic representation;
Figs. 2 and 2a, 3, 4, 5, 6, and 7 each show an
embodiment of hydraulic hammer jars according to the invention
in a half axial section;
Fig. 8 shows an axial section through a portion of the
hydraulic hammer jars according to the embodiment in Fig. 2,
disclosing the locking device of the jars on a larger scale
than in Fig. 2;
Fig. 9 shows a front view of the locking device
illustrated in Fig. 8;
Figs. 10 and 11 show front and side views, respectively,
of the locking device on a larger scale than in Figs. 8 and 9;
; ~ Figs. 12, 13, 14 and 15 each disclose in axial section
an embodiment of a pressure relief valve used in the Figs. 6
and 7 embodiments.
In Fig. 1, the ordinate (m) represents the length of
the represented partial regions of the drill string which
extend upward in any desired length. In the drilling string la
two stabilizers 300,301 are disclosed, with a shock absorber
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302 between them, a drill bit 303 being secured to the lower end
of the drilling string. Directly above the top stabilizer 301,
hammer jars 304 embodying the invention are installed in the dri
stem assembly. In the drilling string lb hammer jars 304 are in-
stalled in the drill stem assembly directly adjoining the shockabsorber 302, which is arranged a short distance directly above
the top stabilizer 301. In drilling string lc, the shock absorber
302 is arranged directly above the drill bit 303, while the hammer
jars 304 are again installed in the drill stem assembly above the
uppermost stabilizer 301. In drilling string ld, the hammer jars
304 are arranged in the upper end region of the drill stem assembly,
a considerable distance from its stabilized portion, while the
shock absorber 302 is located immediately above the top stabilizer
301. Fig. 1 shows that the hammer jars 304 according to the in-
vention can be installed at any point required in the drill string.Beyond that, the hammer jars can also be installed at any point
of the drilling string above the regions represented in Fig. 1.
The hydraulic jars comprises, according to the embodiment of
Figs. 2 and 2a, an inner pipe body 1 whose upper part 2 is pro-
vided at its upper end with a threaded box 3 for connection of the
jars to the adjacent part of a drilling string above it. Axially
extending splines 4 are provided on the circumference of the upper
part 2 of the inner pipe body 1. At its bottom end, the inner
pipe 2 is secured to a central part 5 of the inner pipe body 1.
The upper part of the outer pipe body 6 includes a packing
sleeve 7 having a guide ring 8 on its inner circumference, carry-
ing two spaced sealing rings 9 and a stripper 10, which bear on
the outer circumference of the upper part 2 of the inner pipe
body 1. The packing sleeve 7 has a threaded connection 11 for
~0 securing it to a central pipe portion 12 of the outer pipe body 6,
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which has axial splines 13 of shorter length than the splines 4,
meshing with the splines 4 of the inner pipe body. The splines or
keys 13 permit transmission of the torque between the inner pipe
body 1 and the outer pipe body 6, the greater axial length of the
splines 4 of the inner pipe 1 permitting upward and downward move-
ment of the pipe 1 relative to the outer pipe body 6. Lubricant
can be introduced through an inlet hole 14 in the pipe portion 12
into the annular space 15 formed between the upper part 2 of the
inner pipe body 1 and the portion 12 of the outer pipe body 6,
after which the hole is closed by a suitable plug. The annular
space is closed at the bottom by a compensating piston 16 subject
to the drilling mud surrounding the pipe 12 which can flow through
a port 17 in both directions. The drill mud passes through the
central bore 18 of the inner pipe body 1 and through the bit,rising
in the annular space formed between the drilling string and the
borehole wall.
The central pipe portion 12 is threadedly connected at 19 to
a pressure pipe 20 which has a shoulder 21 acting as an anvil en-
gageable by a percussion piston or hammer 22 of the inner pipe
body 1. The central pipe portion 12 has its lower end threadedly
connected to a bottom sub 12a that has a threaded pin 13 adapted
to be secured to an adjoining box portion of a drill collar or
drill pipe (not shown). The portion 12 has an inwardly directed
valve receiving section 400 through which the percussion piston 22
can pass, as described hereinbelow, as well as a valve sleeve 401
slidably mounted on the central part 5 and also adapted to pass
through a restricted annular portion 402 of the pipe 20 with a
relatively small clearance, so as to constitute an annular orifice
in conjunction with the inner wall 403 of the valve receiving
.0 section. Downward movement of this valve sleeve along the central
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part 5 is limited by its engagement with a valve seat 404
appropriately secured to the central part 5. This central part
also extends downwardly through an annular compensating piston
405 which carries suitable seal rings 406 thereon slidably
sealing against the inner wall 407 of the pressure pipe 20 and
also against the periphery 408 of the central part 5. The
annular space 409 between the inner central part 5 and the pres-
sure pipe 20 constitutes a chamber in which a suitable lubricant
is contained, this lubricant being introduced into the chamber
through a suitable port 410 closed by a plug 411. The pressure
of the drilling mud or other fluid passing downwardly through the
inner pipe 2, 5 can enter the annular space between the inner and
outer members 5, 20, and below the compensating piston 405, to
transfer the drilling mud pressure to the lubricant in the
chamber 409.
Assuming the inner pipe member 1 to be free to move
longitudinally within the outer member 6 and the drilling string
to be stuck in the well bore below the location of the jar, an
upward strain can be taken on the drill string which will
move the innerpipe body structure 1 upwardly until the hammer
22 and valve sleeve 401 pass into the annular region 412
within the valve fitting section 402. When the valve sleeve
enters the valve fitting section, further upward movement
of the inner body 1 within the outer body 6 is resisted,
inasmuch as the lubricant in the chamber above the valve
sleeve can only by-pass downwardly through the annular
orifice around the valve sleeve. A sufficient upward pull
is taken on the drill string and the inner body structure to
` move the valve sleeve through the valve fitting section, but
such movement is relatively slow inasmuch as it is necessary
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1053656
for the lubricant in the chamber above the valve sleeve to
by-pass through the annular orifice. Accordingly, a
preselected tensile pull is taken on the drilling string and
on the inner body 1, the valve sleeve moving upwardly along
the valve fitting section until it enters the enlarged
portion 409a of the chamber above the valve fitting section,
which allows the hydraulic fluid above the valve fitting
section to readily by-pass the valve sleeve, causing the
drill string to accelerate rapidly in proportion to the amount
of the tensile pull thereon, causing the hammer 22 to impact
against the anvil shoulder 21 and deliver a jarring blow to
the outer member 6.
In the event a downward blow is to be imparted on the
drill string or drill collar below the hydraulic jar, it is
merely necessary to lower the drilling string and the inner
body member 1 to cause the downwardly facing shoulder 23 on
the inner member to strike a blow against the upper end or
shoulder 24 of the sleeve 7, this blow being delivered through
the pressure pipe 20 and sub 12a to the drill collar or drill
pipe therebelow.
After the upward jarring action has taken place,
additional impacting of the hammer 22 against the anvil 21 can
occur as a result of first lowering the drill string and inner
body structure within the outer body structure 6, and then
taking a pull on the drilling string and inner body structure
1 to cause the sleeve valve 401 to move through the restricted
valve fitting section 402. Similarly, repeated downward
jarring can take place by elevating the inner body member 1
within the upper body member 6 and then allowing the drill
string to move downwardly rapidly to cause the shoulder 23 to
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deliver a jarring blow against the upper end of the sleeve 7.
Details of the structure and mode of operation of the
floating sleeve valve and the annular orifice between it and
the inner wall 403 of the restricted valve fitting section can
be found in Canadian Patent No. 931,136 and in U.S. Patent
3,880,248. Such details are unnecessary to an understanding
of the several embodiments of the present invention.
In the operating state represented in Fig. 2, in which
the inner pipe body 1 and the outer pipe body 2 are telescoped,
these are locked against axial relative movement by a locking
device 25. The locking device 25 is formed in this embodi-
ment by several, at least two, safety members 26 (Figs. 8 and
9) which are angularly spaced uniformly from each other at the
upper portion of the upper part 2 of the inner pipe body 1 and
the adjacent end of the packing sleeve 7 of the outer pipe
body 6. Each safety member 26 is formed by a bar body 27 with
a central preset breakable region 28 and at its upper and
lower ends with a head 29. The heads 29 of each bar body 27
can be inserted radially into a receiving recess 30 in the
upper part 2 of the inner pipe body 1, and into a corresponding
receiving opening 31 vertically aligned with the latter. The
heads 29 are retained in place by a split snap ring 32.
In the embodiment disclosed in Fig. 3, the hydraulic
jars are installed in the drilling string in an inverted
position relative to the arrangement shown in Fig. 2. In
this arrangement, the downward blows are delivered by the
percussion piston 22 by engaging shoulder 21 (not shown in
Fig. 3) of the pressure pipe 20 of the outside pipe body 6'.
The outer pipe body 6' is here provided with an upper
connecting part 33 which has a female thread 34 for connection
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of the jars with the part of the drilling string above it.
The pressure pipe 20 is threadedly connected at 34a with the
connecting part 33, which forms an annular space 36 with the
upper part 35 of the inner pipe body 1', which is closed at
its underside by a guide ring 37, but which has a passageway
38 for the passage of a scavenging medium, which has access
to the annular space.
Openings 39 are provided in a sleeve 40 which has a
preset breaking point 41 forming the lockiny device 25, whose
bottom end is secured to the upper part 35 of the inner pipe
body 1', and whose top end is secured to a transition piece
42 which bears on a counter-shoulder 43 of the connecting
part 33 of the outer pipe body 6'.
For performing downward blows in the embodiment shown
in Fig. 3 by means of the percussion piston 22, an annular
space 44 is provided between the upper part 35 of the inner
pipe body 1' and the pressure pipe 20 of the outer pipe body
6', which can be filled with a pressure medium through a fill
hole 45 that can be closed by a suitable screw plug 45a. At
the top, the annular space 44 is closed by a compensating
piston 46 to which a reinforcing ring 47 is attached, the
piston being acted on by the pressure medium in the space 44.
A valve seat ring 48 is located in the annular space 44 and
secured to the pipe 1', a valve ring 49 being shiftable on
the body. The ring-shaped percussion piston or hammer 22 on
the upper part of 35 the inner pipe body 1' is disposed below
the valve ring. The annular space 44 has a restricted region
50 of a smaller diameter through which the hammer 22 and
valve 49 move, in a known manner, when the inner pipe body 1'
and the outer pipe body 6' move apart, so that the surrounding
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pressure medium is forced to flow through a narrow ring slot
or annular orifice between the valve 49 and the pressure pipe
wall 403 of the outer pipe body 6'. As soon as piston 22 and
valve have passed relatively through the region 50 of the
annular space 44, the drilling shaft, which is under tension,
acts as a spring and anvil 21 (as in Fig. 2) delivers a heavy
blow against the hammer 20 of the inner pipe body 1'. When
the outer pipe 6' moves downwardly of the inner pipe 1', after
the hammer blow has been delivered, the wall 403 engages the
valve 49 and moves it downward from its seat 48, the pressure
medium flowing around the valve ring 49 through by-pass
channels 51 provided in the upper part 35 of the inner pipe
body 1', which are then in communication with corresponding
radial openings 52 of the valve ring 49.
In the operating state represented in Fig. 3, the inner
pipe body 1' and the outer pipe body 6' are initially locked
by the safety sleeve 40 in their telescoped position. The
taking of a sufficient upward strain on the outer body 6' by
the drilling string disrupts the sleeve at i.s weak section 41,
permitting the inner and outer body members 1', 6' to move
longitudinally with respect to each other.
The embodiment shown in Fig. 4 can be considered as a
bottom extension of the embodiment illustrated in Fig. 2.
Instead of the safety members 26 being designed as bar bodies
in the upper portion of the inner pipe body 1, a safety
sleeve 53, having a preset breaking point 54, forms the
locking device 25, which locks the inner pipe body 1 and the
outer pipe body 6 in their telescoped position. The safety
sleeve 53 is secured at its upper end to the lower end of the
central part 5 of the inner pipe body 1. It has a flange or
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abutment shoulder 55 disposed under the lower end of a
connecting pin 57 provided with a male thread for connection
with the drilling string below the jars. The pin forms the
lower portion of an outer pipe section 56 threadedly secured
at 58 to the pressure pipe 20 of the outer pipe body 6. An
annular space 60 can be charged with a liquid medium flowing
from the center passage 18 through one or several radial
openings 59 in the safety sleeve 53, and is closed at its
upper end by a guide ring 61 having passageways 62 for
admitting the compensating fluid into the lower part of the
annular space for action upon the piston 46. Since the jars
perform upward blows by means of the percussion piston 22 in
the arrangement disclosed in Fig. 2, the hydraulic fluid
enters through the fill hole 45 to fill the annular space 44
in which the valve seat ring 48, the valve ring 49, the ring-
shaped percussion piston 22 are located, the space 44
including the region 50 of reduced diameter. The hammer
shoulder or anvil 21 of the pressure pipe 20 is above the
restricted region 50.
The embodiment shown in Fig. 5 differs from the Fig. 4
embodiment, particularly with regard to its assembled
condition in the drilling string. It has a different design
of locking device 25, which is formed in this embodiment of a
safety sleeve 63 having a preset breaking region 64, the
sleeve being secured to the lower end 65 of the lower part 5of the inner pipe body 1, and being spaced from the outer pipe
section to form an annular space 60. The safety sleeve 63 is
likewise provided with one or several radial openings 66 for
the passage of the compensating medium into the annular space
60 for action against the compensating piston 46. The locking
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of the inner pipe body 1 to the outer pipe body 6, in the
represented telescopic position, is effected by a clamping
wedge locking mechanism 67, which secures the lower end portion
of the central part 5 and the lower connecting part 56 of the
outer pipe body 6 against axial extension.
To this end, an intermediate ring 68 is secured to the
lower part of the safety sleeve 63, and also to a separate
. abutment sleeve 69 extending coaxial of the safety sleeve 63,
- the sleeve 69 having a conical wedge surface 69' spaced below
the intermediate ring 68. The abutment sleeve 69 is
surrounded by a compression spring 70 which engages the lower
pressure surface of the intermediate ring 68 and bears on the
top side of clamping wedges 71 which are arranged between the
wedge surface 69' of the abutment sleeve 69 and the inner
surface of the connecting part 56 of the outer pipe body 6.
In the embodiments of Figs. 2 to 5, if a drilling pipe
string gets stuck in the borehole and must be loosened by
blows, a predetermined pull, that is, an overload, which is
introduced into the drilling string by pulling on the latter,
is produced by the operating personnel at the drilling
installation between the inner pipe body 1, 1' and the outer
pipe body 6, 6', by which the safety members 26 and the
safety sleeves 40, 53 and 63, respectively, are disrupted, so
that the lock effected by the locking device is released and
the inner and outer pipe bodies can move apart to perform
upward or downward blows by means of the percussion piston 22
of the inner pipe body 1, 1' striking against the abutment
shoulder 21 of the outer pipe body 6, 6'. Naturally, a
corresponding locking of the inner pipe body 1, 1' and of the
outer pipe body 6, 6' can be effected again by using new
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safety members 26 or safety sleeves 40, 53 and 63 at thedrilling installation, after the drill pipe string has been
pulled from the well bore.
The embodiment shown in Fig. 6 differs from that of
Figs. 4 and 5, with regard to the representation and
arrangement in the drilling string, merely by a different
design of the locking device 25. For the provision of the
locking device 25, an additional closed annular space 72
filled with pressure medium is provided, according to the
embodiment in Fig. 6, in the lower portion of the jar between
the central part 5 of the inner pipe body 1, which is
extended in this embodiment down to the lower portion of the
jars. The connecting part 56 or the outer pipe body 6 is
closed at its bottom end by a ring-shaped piston 73 which
bears with its end face remote from the annular space 72 on a
stop ring 74 secured to the inner pipe body 1. The upper end
of the annular space 72 above the piston 73 is closed by a
gasket 75. The annular space 72 can communicate with the
annulus surrounding the outer pipe body 6 through a pressure
relief valve, generally designated 76. The pressure relief
valve 76 opens only at a predetermined excess pressure of the
pressure medium enclosed in the annular space 72, which is
produced by the operating personnel at the drilling instal-
lation by pulling on the drilling string when the latter gets
stuck in the borehole. As long as the pressure relief valve
76 is closed, axial relative movement of the inner pipe body 1
with regard to the outer pipe body 6 cannot occur since the
- pressure medium in the annular space 72 functions as a
hydraulic lock. Only when the pressure relief valve 76 opens
is a working stroke of the hammer jar, that is, a relative
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separating mcvement of the inner pipe body 1 with respect to
the outer pipe body 6, possible by the resulting communication
of the annular space 72 with the region surrounding the pipe 6.
One or several radial openings 45, closed by suitable plugs,
are provided in the pipe 20 for admitting fluid into the
annular space 44 for action on the compensating piston 46.
The piston 73 can also be subjected to the fluid medium in
the central duct 18 through an annular slot formed between the
stop ring 74 and the connecting part 56 of the outer pipe
body 6, and thus takes over a compensating function at the
same time.
In the modified embodiment of a hydraulic locking device
25 shown in Fig. 7, the bottom of the additional annular space
72 is filled with pressure medium and is closed by a ring-
shaped piston 78 which bears on a stop ring 79 secured to thepart 5 of the inner pipe body. Below piston 78, several radial
openings 80 are provided in the pressure pipe 20 of the outer
pipe body 6 for admission of external fluid into the space 72
for action against the underside of the piston 78. In the
upper end region of the connecting part 56 of the outer pipe
body 6 is arranged a gasket 81 between the latter and the
outer circumference of the part 5 of the inner pipe body, the
upper end of the annular space 72 above the piston 78 being
closed by an axially displaceable, ring-shaped intermediate
piston 82 which closes the lower end of the annular space 44
filled with pressure medium, the space 44 surrounding the
percussion piston 22 and the valve ring 49 with its modified
valve seat 48'. At 83 is shown a modified pressure relief
valve, of which several, arranged uniformly around the
0 circumference of the outer pipe body 6, can be provided
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l(~S3~S6
according to Fig. 7. Pressure relief valve 83 has a housingpart 84 projecting radially into the additional annular space
72 which forms a lower stop for the intermediate piston 82.
After the pressure relief valve 83 has opened and a blow has
been performed, the housing part 84 forms an upper stop for
piston 78, just as the piston 73 bears on the upper shoulder
56' of the connecting part 56 of the outer pipe body 6, in
the comparable state in the embodiment according to Fig. 6.
In the embodiments shown in Figs. 6 and 7, the pull
introduced by the operating personnel is transmitted from the
inner pipe body 1, through the stop rings 74 and 79 to the
pistons 73 and 78, respectively, so that a pressure increase
is produced in the annular space 72 proportionally to its
piston surface, which leads to the opening of the pressure
relief valves 76 and 83, respectively at a predetermined upper
limiting pressure value. Due to the resulting communication
of the annular space 72 with the region surrounding the jars,
the hydraulic lock between the inner pipe body 1 and the
outer pipe body 6 is released and the jars can perform a first
working stroke for an upward blow, in the embodiments
according to Figs. 6 and 7, by means of the percussion piston
22 striking the anvil surface 21 (Fig. 2). During this first
upward stroke of the inner pipe body 1 with regard to the
outer pipe body 6, there is a certain damping action present
to prevent sudden bursting of the preset breaking point of a
safety member or safety sleeve, which results in a gentle
transition to the working stroke.
Fig. 12 shows an embodiment of the pressure relief
valve 83 where it has a valve opening 85 closed by a
0 rupturable disc 84. The rupturable disk 84 consists of a
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thin metal plate which ruptures at a predetermined pressure.Rupturable disk 84 rests on a retaining ring 86 and is secured
in the valve housing 87 by means of a threaded sleeve 88
screwed into the valve housing 87. The valve housing 87 is,
in turn, screwed by its threaded portion into a threaded bore
of pressure pipe 20 and has the housing part 84a projecting
radially into the annular space 72. While the rupturable
disk 84 is represented in the unbroken state, the pistons 78
and 82 are shown (Fig. 12) in a position in which they bear on
the housing part 84a of the pressure relief valve 83.
Fig. 13 shows a modified pressure relief valve 83',
which likewise has a valve opening 85 closed by rupturable
plate 84 but where the rupturable disk 84 resting on the
retaining ring 86 is secured in place by means of a sleeve 88
threaded directly into a corresponding bore of the pressure
pipe 20.
In the embodiment according to Fig. 14, the pressure
relief valve is designed as a spring-loaded non-return valve
89, whose housing 90 is screwed into a bore of pressure pipe
20, just as in the embodiment according to Fig. 12, with the
projecting housing part 84a serving as a stop for the pistons
78 and 82. The valve opening 91 is closable by means of a
ball 92 against which a compressed spring 94 bears, put under
compression by a pressure sleeve 93 screwed into the housing 90.
In the varient according to Fig. 15, the non-return
valve 89' has a modified spring compression sleeve 95 screwed
directly into a bore of the pressure pipe 20. A compression
spring 96 is arranged in this embodiment between the inner
end face of the sleeve 95 and a valve ball 98 closing the
valve opening 97.
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~)53~
The pressure relief valve 83' and the non-return valve
89', respectively, can be used in the embodiment according to
Fig. 7, in which the pressure relief valve, or several pressure
relief valves distributed in a uniform angular relation over
the circumference of the pressure pipe 20, are generally
designated 83.
While the design of the pressure relief valves with
rupturable disks has the advantage that the excess pressure
necessary for opening the valves can be determined very
accurately, the design as a spring-loaded non-return valve
has the advantage that the flow of the surrounding fluid
medium into the annular space 72, after the opening of the
valves and the release of the lock, is prevented. Beyond that
it offers the possibility of releasing the jars only for a
limited extension movement between the inner and outer pipe
bodies by allowing only a part of the pressure medium contained
in the annular space 72 to flow through the valve with the
overload necessary for opening the pressure relief valves by
pulling on the drilling string at the drilling installation and
restoring the lock again to prevent a further separating
movement of inner and outer pipe bodies by pulling on the
drilling string with overload. Instead, it is also possible
to fill the annular space 72 only partly with the pressure .
medium, with the result that the jars permit a relative
movement of the inner and outer pipe bodies, as is required
for the imposition of blows imposed by the percussion piston
22 against the anvil 21. Such a design is of particular
advantage if upwardly directed. Gravity dependent blows are
to be exerted by moving the drilling string up and down to
overcome any resistances in the borehold during the lowering
- 20 -
. . - ' -. ' : ' .:
~n53{;s~
of the drilling string, that is, when the jars are to be used
as a buffer bar or a so-called bumper.
The foregoing detailed description of a number of
embodiments does not exclude numerous possible variations in
the design and arrangement of the locking device between the
inner and outer pipe bodies. Thus, for example, an embodiment
of the jars can be provided by inverting the Fig. 2 embodiment,
with an outer pipe body connected to the upper part of the
drilling string, the locking device being similar to the
embodiment in Fig. 2, and to arrange it correspondingly
between the lower connecting end of the inner pipe body and
the lower part of the outer pipe body. Furthermore, a
hydraulic design of the locking device can be provided as a
variation of the embodiments according to Figs. 6 and 7, the
outer pipe body being connected with the upper part of the
drilling string and the inner pipe body connected with the
lower part of the drilling string. In a variant of the
embodiment according to Fig. 3, such jars can also be designed
for the performance of upward blows by inverting the jars, in
which case it suffices principally to design the hammer
system as it is represented in the embodiments of Figs. 4 and
5 and Figs. 6 and 7, respectively.
Finally, it is also possible in a mechanical locking
device to arrange the locks and the jars not only in the
fully retracted position, but also in an intermediate position
in which the inner and outer pipe bodies are displaceable to
a limited extent between a fully telescoped and partly
separated position. This is possible, for example, by
extending the bar body 28 (Fig. 2) and designing the openings
30 30, 31 as axial slots, or by extending the safety sleeve 53
- 21 -
lOS~56
(Fig. 4), or by extending the safety sleeves 40 (Fig. 3) and
67 (Fig. 5), respectively, and securing them on the inner or
outer plpe body by means of a limited sliding guide.
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