Note: Descriptions are shown in the official language in which they were submitted.
:
610~
I'he invention relates to a shock absorber for deep
hole drill pipe which can be installed in the pipe coaxially as
an intermediate part in vertical alignment and comprlses an outer
pipe part and an inner pipe part which are movable coaxially
relative to each other but are secured against twisting by torque
transfer means disposed in the upper shock absorber area, defining
between them an annular chamber filled with hydraulic fluid and
supporting ring-shaped spring elements stacked one on top of -the ~ -
other in said annular chamber for shock absorption with shock
attenuation, the annular chamber being sealed by an upper seal
and a lower seal, of which the lower seal is coordinated with an
equalizer piston which is independently movable coaxially within -
limits between the outer and the inner pipe parts, its bottom
side closing off an equalizing chamber for the hydraulic fluld in
the annular chamber.
In one kno~n shock absorber of this type, the spring
elements consist of flat washers made of an elastomer material,
in particular polyurethane, s-tacked on top of each other to form
a single column by interposing metal absorption discs. The elastic
deormability of the elastomer rings imparts to such a shock
absorber strokes from about 30 to 100 mm, depending on the design,
at a desired soft spring characteristic and a favorable attenuating
action resulting from the self-darnping properties of the elastomer
materia.l. The hydraulic fluid in the annular chamber which accom-
modates at the same time the torque transfer means, due to theequalizer piston, operates at the flushing pressure in the drill
pipe, is effective as lubricant in the area of the torque transfer
means formed by a tongue and yroove system and performs, among
others, a pressure equalizing function in the annular chamber
relative to the pressures in both the flushing circulation and the
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drill llole, the equalizer piston automatically brlnyiny about a
matching of pressures and, if necessary, absorbing occurring
.~ .... ..... ...
hydraulic fluid losses. : :
Such shock absorbers, designed to dampen the drill bit
vibrations reacting on the driLl pipe and to reduce the high -.
dynamic stresses of the drill pipe resulting from such vibrations : .
as well as to equalize the drill bit pressure in the interest of .
increased.drilling speed, have proven out well in both deep and ,
shallow holes within wide speed ranges and also under difficult ~... .. -
lO drilling conditions, but their application is restricted to holes .. .
ln which drill hole temperatures of about 100 to 130C are not
exceeded and relatively large outside diameters of the drill pipe ~ . ;
; and thence of the shock absorber are not fallen below The .. : .
flushing pressure in the drill pipe also limits their applicability
because this flushing pressure acts upon -the hydraulic fluid in the
....
. .:
annular Fhamber and this pressure generates in the hydraulic fluid -~
: an axially operating expansive force between the outer and the ~.:
inner pipe parts which may exceed the drill bit load and lead to ;.
~ the outer and inner pipe parts being driven apart and the shock .~ . .
,:~ :',. . : '
absorber acting like a relatively rlgid element.
: It is an object of the invention to provide a shock .. : .
absorber of the kind described at the outset which, with improved
spring and damping characteristics, can also be applied in ~the
: high temperature range and can be built with reduced cross-
: 25 sectional dimensions.
To solve this problem, the invention provides in the
first place that the spriny elements are divided.into at least two
parallel-acting spring columns mutually superposed with axial
spacing, that they are housed in spriny chambers of the annular
30 chamber so as to communicate with each other in flow connection ..
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and that they are formed of dish-~ype sprinys of steel or a sirnilar
metal, combined within each spring column into a number of equally
stacked packets whose stacking sense alternates from packet to
packet in axial direction.
The shock absorber according'to the invention is largely
independent of temperature in its spring and damping characteristics
and can be used without problem in the range o~ drill hole tempera-
tures reaching or exceeding 300C. Having two or more paralleled
spring columns divide the occurring shock loads among themselves
reduces the loads to be absorbed by the spring elements within one
column so that springs, each having a shorter spring travel, can
be designed -to have smaller radial dimens1ons, permitting the
construction of shock absorbers having an outside diameter of ~-3/4
' ' inches, for example. Even in shock absorbers of such small cross-
sectional size, the spring elements are not subject to the danger
~ of destructi~n by breakage while assuring, furthermore, uniEormly
:: .
good attenuation through friction work for a wide range of strokes. ~ ~ '
In addition, the shock absorbers accordiny to the invention provide
the possib'ility of varying stroke, spring characteristic and damping
characteristic by changing, for instance, the number of springelements stacked the same way in one packet and adjusting them to
the respectively prevailing drilling conditions.
According to a further development, each spring chamber
can form a pumping chamber of decreasing volume when the outer and
inner pipe parts retract and of increasing volume when they extend
so'that, during the operation of the shock absorber, alternating
axial flow motions are impressed on the hydraulic fluid which can
be utilized to achieve particular damping characteristics,
espec1ally when, in further development of the invention, at least '
one flow damper for the hydraul.ic fluid flowiny under the pumping
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action of the chaMbers is provided between chambers of the annular
chamber.
Such a flow damper may be formed by giving connecting
channels between the chambers in the annular chamber generating a
pumping action suitable cross-sectional dimensions, or by defined
constrictions in the path of the hydraulic fluid flow,,such .. ; .
dampers exer:ting, when filled with hydraulic :Eluid, the same
damping action upon it in bokh flow directions. However, in cases
where dlfferent damping actions are desired for the retraction and
10 extension of the outer and inner pipe parts, there is also the ::.
: possibility of providing by means of check valves o.r the like, . .: :
,. . .
throttling points along the path of the hydraulic fluid flow to ~ .
have different damping actions as a function of -the respective
.
flow direction of the hydraulic fluid
. ''.::' :
~15 ~ In connection with or independent of an embodiment of ~.:
: ~ the kind described above~ the inventlon provides ~urther that the :~ ~ -
: annular chamber for the spring elements is closed off by its upper
seal at a dlstance below the torque.transfer means and that the
~ torque transfer means, in turn, are disposed in a separate,
:~ 20 hydraulic fluid-filled annular chamber between the ou-ter and the
inner pipe parks which chamber, in turn, is closed off by an upper
seal and a lower seal, of which the lowe.r seal is coordinaked with
:~ an upper equalizer piston which is independently mo~able coaxially ~.
.
within limits between the outer and the inner pipe parts, iks
bottom side closing off an equalizing chamber for the hydraulic
: fluid, and below which is located between the outer and the inner
pipé parts an intermediate chamber communicating with the flushing
area of khe drill hole through connecting holes
Such a design reduces the danger of the occurrance of :
socalled "through flushinys" on the one hand and the axial hydraulic
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. ~ 10~76100
, . .
expansion forces operating between the outer and the inner pipe
parts on the o-ther, and that in particular when, according to the
invention, the outside diameter of the inner pipe part is smaller
in the area of the upper seal of the annular chamber Eor the spring
elements than the outside diameter of the inner pipe part in the
area of the upper seal of the annular chamber for the torque
transfer means.
A further reduction of the hydraulic expansion forces
can be achieved by making the outside diameter of the inner pipe
part smaller in the area of the equalizer piston below the annular
chamber for the spring elements than the outside diameter of the
inner plpe part in the area of the upper seal for this annular
chamber, when an end chamber communicating through connecting holes
with the drill hole is provided below this lower equalizer piston
between the outer and the inner pipe parts and when a seal is
inserted between the outer and the inner pipe parts below this end
;~ chamber
Numerous additional features and advantages follow from
the claims and the specification in connoction with the drawing in
which several embodiment examples o~ the subject of the invention
are illustrated in yreater de-tail.
Fig. la shows the upper,
Fig. lb the central and
Fig. lc the lower part of a shock absorber according
to the invention in an axial half-section.
Fig. 2 shows, in a section similar to Fig. lb, the
upper area of the lower spring chamber of the
annular chamber between the outer and the inner
pipe parts in an enlarged partial view,
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Fig. 3 is a view similar -to Fig 2 oE a modified
embodiment,
Fig. 4 an enlarged view of a cross-section along line ~-
IV-IV in Figs. lb and 5 respectively, ~ ~
Fig 5, in larger scale, a partial view of a shock ~ ;
absorber in the area of line IV-IV in Fig. lb and :
Fig. 6 a broken-off view of the lower area of the
shock absorber according to the invention in an
embodiment modified according to the invention.
10 ~ The shock absorber shown in Figs, la to lc which are a
continuation of each other consists, in detail, of an inner pipe` ~ ~ ~
part 1 and a~n outer pipe part 2 The inner pipe part is composed ~ ;
of;an upper section 3, a central section 4 and a lower section 5.
The upper end of the upper section 3 is provided with an internally
15 ~threaded coupling 6 for connection to the lower end o~ a drill
plpe section, and~is screwed to the central seation 4 in the area
of a tapered screw connection 7. In turn, the central section 4
is assembled to the lower portion 5 in the area of a tapered screw
connection 8. These sections 3, 4 an~d 5 of the inner pipe part l
jolntly enclose a central flow-through channel for thq flushing
ciraulation.
; ; The outer pipe part 2, in turn, consists in detail of
: . .
an upper section 10, two central sections 11 and 12 and a lower
;~ section 13. In the area of a tapered screw connection 14, the,~ . :....... .
upper section lO is joined to the central section ll and it, in
the area of a tapered screw connection 15, ta the next lower
section 12. The central section 12 and the lower section 13 of
the outer pipe part 2 are connected through a tapered screw
connection 16 The lower end of the lower section 13 has an
externally threaded connecting pluy 17 for screwing to the upper
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encl of a lower drill pipe section.
The inner pipe part 1 and the outer pipe part 2 which
encloses the Eormer coaxially define jointly an annular chamber ~-
18, the upper end of which is closed off by an upper seal 19
Above it is a fine wiper 20 and above the latter a coarse wiper 21.
Let into the upper section 10 of the outer pipe part 2 below the
seal 19 is a wear ring 22. At its underside, the annular chamber
18 is closed off by an equalizer piston 23 which is coaxially
movable within limits between the outer pipe part 2 and the inner
10 pipe part 1, independent of the latter, its bottom end closing off
an equalizing chamber 24 of the annular chamber 18 The equallzer
piston 23 carries on its outside and its inside seals 25, 26 again
preceded on the underside by fiAe wipers 20 and coarse wipers 21.
The underslde of the equalizer piston 23 faces an end chamber 27
15 between the inner pipe part 1 and the outer pipe part 2, forrning
a continuation in space of the equalizing chamber 24 and communi-
cating, in the shock absorber design according to Figs. la to lc,
with the central flow~through channel 9 for the flushing circulation
through an axial connecting channel 28.
The annular chamber 18 is ~illed with an hydraulic
fluid filled in, for example, at normal pressure through a closable
inlet hole 29 above ground. Duriny the operation Oe the shock
absorber, the equalizer piston 23 impresses on this hydraulic `
, :,
fluid the pressure in the 1ushing circulation in the shock
25 absorber design according to Figs. la to lc.
As may be seen from Fig la, due to the particular ~ `
arrangement of the seal 19, the annular chamber 18 ends a distance -
,
below a toryue transfer means 30 ~ormed by a tongue and groove
system and assuring that, in the event of coaxial relative
30 motion of inner pipe part 1 to outer pipe part 2, these two pipe ~ `
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~ 6~00 : :
,.. ~`~ parts are secured against twisting. This torque transEer means 30,
disposed in the upper shock absorber area, is in turn arranged in
a separate annular chamber 32 which is located between the inner .
pipe part 1 and the outer pipe part 2, can be filled with hydraulic
.- - . - .
, fluid through a closable inlet hole 31 and is closed off by an ` .
~ . .. . .
upper seal 33, above which is again a fine wiper 20 and a course
wiper 21. Let into the upper section 10 OL the outer pipe part 2 .:.
below the upper seal 33 is again a wear ring 22. The lower closure
of the upper annular chamber 32 is formed by an upper equalizer
piston 34 carrying on the inside a seal 35 with a fine wiper 20
: dlsposed below it, and on the outside a seal 36 with fine wiper 20
and course wiper 21 disposed below it. ~he underside of this equal-
: ~ izer piston 34 closes an upper equalîzing chamber 37 and faces an .intermediate chamber 38 between the inner pipe part 1 and the outer
L5 pipe part 2 which, as it were, forms the con-tinuation in space
of the upper equalizing chamber 37 and communiaates with the drill ~ -:
hole through connecting holes 39. Accordingly, the pressure in the
.
::flushing circulation in the drill hole, which is smaller by the
drill bit loss than the pressure in the flushing circulation in
,
~; 20 ~ the drill pipe, acts upon the underside of the equalizer piston 34.
,,, j ' !
Therefore, the pressure of the flushing circula-tion in the drill
hole is impressed on the hydraulic fluid in the annular chamber 32. .: :
Since only the smaller cross-sectional area of the diameter : ;
41 is acted upon by the flushing pressure prevailaing in t-he .:::
: ~ .
: : '5 annular chamber 18, and not the cross-sectional area of the .:
larger diameter 40 in the area of the seal 33, the resultant
hydraulic-expansion force in axial direction is considerably
reduced and tends to a correspondingly lesser degree
-- 8
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76:1()0
to drive the inner pipe part 1 and the outer pipe part 2 apart.
In addition to the equalizing chamber 24, the annular
chamber 18 has an upper spring chamber 43 and an additional upper
chamber 44. All chambers 44, 43, 42 and 24 are interconnected by
flow-through channels, of which those connecting the upper spring
chamber 43 and the upper end chamber 44 have the reference numeral
,
45, those connecting the upper spring chamber 43 and the lower
spring chamber 42 the reference numerals 46 and 47, and those
connecting the lower spring chamber 42 and the lower equalizing
chamber 24 -the reference numeral 48. The insides and outsides of
all chambers of the annular chamber 18 are bounded~by coaxial
cylinder surfaces of the inner pipe part 1 or the outer pipe part
2, respectively. The top side of the upper end chamber 44 is
.
limited by an inwardly projecting shoulder 49 of the outer pipe
part 2 and its bottom side by an outwardly projecting shoulder 50 -
~of the inner pipe part 1. The limit of the top side of the spring
..
chamber 43 is formed by an outwardly projecting shoulder 51 of the
inner pipe part 1 and the limit of the bottom side by an inwardly
projecting shoulder 52 of the outer pipe part 2. The corres-
. ~
20 ponding limiting shoulders for the lower spring chamber have the -
reference numerals 53 and 54, respectively, Due to this design,
; ~` the chambers 44, 43, 42 form pumping chambers which e~perience
changes in volume by the retraction and extension of the inner pipe
part 1 and the outer pipe part 2 during the functioning of the
shock absorber in the drilling opera-tion, with the result that the
hydraulic fluid in the annular chamber 18 is caused tc perform
alternating flow motions, This function is essential, in parti-
cular for the spring chambers 43 and 42. The upper end chamber 44
forms a supplemental chamber which can possibly be dispensed wi-th.
Accomodated in the spring chamber are spring elements -
_ g _ .
. . .
in the form of dish type springs 55 (spring chamber 42) and 56
(spring chamber 43). These dish type springs, preferably made
of steel, are stacked inside each spring chamber to form a
spring column, the dish type springs within each spring column
being combined into a number of packets, stacked the same way,
the stacking sense alternating in axial direction from packet
to packetO It is preferred when four dish type springs each
are stacked the same way to form one packet, it being possible
to provide as many as 38 such packets in each spring column,
for example. The inside and outside diameters of the dlsh type
springs are normally the same within one spring column. ''''.`.'!'
The inside and outslde diameters of the dish type
springs are such that they are penetrated by the inner pipe
,:
part 1 and enclosed by the outer pipe part 2, both leaving a -
circumferential gap. The dish type springs 56 of the upper
spring column 58 are supported between a lower supporting ring -
59 on top of the shoulder 52 and an upper supporting ring 60
under the shoulder 51. The dish type springs 55 of the lower
spring column 57 are supported in the same manner between a
; 20 lower supporting ring 61 on top o~ the shoulder 54 and an upper
supporting ring 62 under the shoulder 53. In the embodiment
example according to Figs. la to lc, the peripheral surfaces of
the supporting rings are flush with the respective shoulders.
In the operation of the shock absorber in its design
according to Figs~ la to lc, the dish type springs of the parallel-
acting spring columns 57, 58 absorb the shock load caused by the -
retraction of the inner pipe part 1 and the outer pipe part 2 by ;
a deformation reducing their cone angle, a part of the shock
energy being destroyed and converted to heat by friction along the
mutually ~acing dish spring surfaces in engagementO In addition to
the damping resulting therefrom, a damping is brought about by
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means of the h~draulic fluid which, due to the pumping action of
the spring chambers 42, 43, flows in the flow-throuyh channels 45,
46, 47 and 48 and are subjected to a throttli.ng action during this
flow motion. For this purpose, the cross-sectional flow areas of
5 the channels 45, 46 and 48 are designed so that the desired damping
effect is impressed on the hydraulic medium flowing through them.
Accordingly, when the flow-through channels 45, 46 and 48 are - .
designed to have a constant flow section over their axial length
as in the example per Figs la to lc, they form over their entire
lO axial length damping sections in whiFh the throttling effect and, : .
therefore, the hydraulic damping occurs ln both the retraction .~: -
and extension of the inner pipe part 1 and the outer p'ipe part 2. .:
Instead of such axially long damping sections there is also the
possibility of providing defined damping sections of shorter axial ;..
lS length which may be formed by giving the flow-through channels a
constricted damping section over an axially limi-ted portion of
. their length only, but designing them otherwlse so as to offer no `.; ~
or only a small damping resistance to the flowing hydraulic fluid. :. -
This is shown by way of example in Fig. lb in whlch the flow~
: 20 through channel 47 has such a wide flow section while the defined . ~ :.
damping point is formed by the upper supporting ring 62 of the : :
lower spring chamber 42, the out.side diame-ter of said ring and the
inside diameter of the opposite area of the outer pipe par-t . . .:
: (section 12) enclosing a damping gap 63. Such a design may be
25 provided, for instance, also in the area of the supporting rings : ~ .:
59, 60 and 61, in which case the connecting channels 45, 46 and 48, ..
respectively, are given a correspondingly wide cross section. .
A modified design is depicted in Fig 3 in which the
supporting ring 62, its inner and its outer periphery sealed by .
means of seals 64, is interposed between the inner pipe part l and ~
- 1 1 - .'
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~ 1076~0C~
`; the outer pipe part 2 and has flow-through channels 65 forming a
damper when hydraulic fluid flows through them upon the retraction
,
of the outer and inner pipe parts. In addition, the supporting
ring 62 has flow-through channels 66 offering no or reduced damping
effect when hydraulic fluid flows in one direction (from top to -
~bottom) and blocking the flow in the opposite direction by means
of a check valve 67. Such a design provides for a damping effect
by damping the hydraulic fluid only when flowing in one direction,
whereas in the opposite flow direction there is no damping action
or only to a reduced degree This makes it possible to vary the
damping effect for the retrac-tion of the inner pipe part 1 and ' -- ; ''
the outer pipe part 2 from the damping effect for their extension.
The design o the flow damper ln Fig. 3 is only an example to -
illustrate the possibilities for varyi.ng the damping effect as a ''
: ::
15 function of the motional directions of the shock absorber pipe ' ' -
parts It goes without saying that all suitable valve designs may
be employed, it being possible also to provide flow-through channels -
66 in the supporting ring 62 only which can'then be closed more by
the valves when the hydraulic medium flows in one direction rather ''
.
20 than in the other. '
Fiy. 6 shows a modification in the lower shoclc absorber'
area, where there is provided below the lower equalizer piston 23
which is only indicated schematically in Fig. 6, an end chamber ~
27' which communicates with the drill hole through connecting holes ~''~ '' '
;
70 'and is sealed ayainst the central flow-through channel 9 for the
flushing circulation For this purpose, there iG inserted between ~-
the lower end of section 5 of the inner pipe part 1 and the lower
section 13 of the outer pipe part 2 a seal 71 to close off the
lower end of channel 28. This seal 71 is located in an area of
even smaller diameter t'han the diameter 51 Eor the upper seal 19
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thereby achieving, in view of the communication oE the chamber 27'
with the flushing circulation in the drill hole, a further ~ecluc-
tion of the expansion forces operating between the inner pipe
part l and the outer pipe part ~.
It is a matter of course that numerous modifications
are possible within the scope of the invention. For instance,
instead o two superposes spring columns 57, 58, three such
¦ parallel~acting columns can be arranged on top of each other.
Also, the number of dish -type springs stacked in the same sense in
one spring packet can be decreased or increased to suit the
desired damping effect. This applies naturally also to the
number of spring packets provlded in each spring column. Further-
more~ the engaging surfaces of the dish type springs can be ;~
provided with a wear-reduc1ng coating such as of tetrafluorethy-
lene. In cases where relatively easy drilling conditions prevail,
the provision of flow dampers for the hydraulic fluid in the annu-
lar chamber 18 may also be omit-ted if the natural damping of the
dish type springs suffices due to their friction during the
functioning of the shock absorber. Instead of arranging the torquc i
,
transfer means in the upper shoc]c absorber area, it is also
possible to provide it in the lower area. ~
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