Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
P~EI)UCTTON UN;tT O~ LI,IhG ~qO'i'OR
~ he prese~t i~vention relates to drillin~ industry and,
more particularl~ to 'he reduction u~,ts of drilling motors.
Mos-t ef~ecti~le~g the prese~t invention will be employed
~or drilling deep oil and gas wells~ though it will also prove
~seful in m~.ni~ industry and in the field of construction.
q~he use of reduc-tion units in clrilling motors is not a
rbol~ l l l s
noveltg. One of the f rst ~xbc~ incorporated a planeta-
xy reduction gear in~t~elc1 between the operating element,
i.e~ tuxbine, and the supporting membe~ intended to txansmit
the weight of drill pipes to the bit. q'he reductio~ gear was
located in an oil-filled ch~mber. ~he chamber seals had the
form of packed glands with intermediate metal rings. ~he
b~.sic disadvantages of the device were the absence o~ tho
mea~s fox ~educing the pressure drop in the lubricator seals
and a low durability of ~aid seals under the specific working
conditions of well bottom drilling. Hence, the efficiency of
the reduction gear wa8 very low and the sex~ice life failed
to reach 10 hours eve~ at a low power developed by o~e stage
of the turbodrill.
The basic factors affecti~g the performa~ce of the reduc-
tion unit in the course of drilling are ~s ~ollows.
~ o ensure efficient fu~ctioning of the rock-breaking tool
it i~ necessary to transmit high power and torgue ~rom the
power generating eleme~ts to the well face at a limited
diameter of the drilli~g motor. ~hus, with the motox diameter
of 195 mm the tor~ua applied to the bit i~ the course of
drilli~g amou~ts to 300 500 ~gfm.
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iO98i~0
Due to the an~sotropy of the drilled roC~9 the surEace
irregularities o~ the wall fac~ and the toothed surface o~
the bit cu~ters, the bit is subjected to heavy axial
vibrations together ~Jith the drilling motor. ~his i5 accompani-
~d b~ Yluctuation~ o~ torque~ the am~litude of ~aid
~luctuation~ reaching and even 0xceedin~ t~ice the value of
the above-~pecified avexage torque. I~ the last case the bit,
and consequently~ the elements of the reduction gear ma~ start
rotating in the revexse direction.
Operation of the d~illing motor is also accompanied b~
strong radial vibratioDs which cause bending of the basic
motor parts, i.e. casings and ~hafts whose longitudinal di-
mensions are considerably longer tha~ the lateral dimensions
of the motor parts, this bringing about axial misalignment
of the coupled motor shafts and heavy radial loads imposed on
th~ir support~.
~ he process of drilling presuppofie~ the use o~ a drilling
fluid containing hard abrasive particles ~hich cause rapid
wear of the reduction gear. When the reduction gear is sealed
in a~ oil-~illed chamber protected by seals, the seals proper
become intensively worn. ~his process is a~gravated bg pulsat-
so
A io~s in the fluid pressure ~e that the particles containedi~ the ~luid are periodicall~ forced into the gaps between
the seals.
~ he above-listed ~actors pro~e that neglect of any one of
them cuts down the ~ervice li~e of the reductio~ unit; therefo~a
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1~)98110
provision of an efficient and durable reductlon unit of a drilling
mo~or can be achieved exclusively by a comprehensive solution
of the problems posed by all these factors.
At present there is known a nurnber of types of
retlllc~lon units of a drilling motor.
Known in the previous art is a reduction of a drilling
motor comprising a casing, input and output shafts mounted
on supports, a planetary reduction gear accommodated in an oil-
filled chamber provided with an oil-protec~ion system consisting
of face seals which are better adapted for face-drilling
conditions than the packed glands. The input shaft is coupled
with the reduction gear by a splined sleeve while the output
shaft is connected to the pinion carrier of the planetary
reduction gear by a screw joint. The channel for the drilling
fluid has the form of central holes in the reduction unit
shafts.
A disadvantage of this prior art reduction unit lies
in that said unit can be employed only in such drilling motors
whose actuating elements have an oil-protection system of their
own, for example in electrodrills, because the reduction unit has
no seal on the input shaft. The output shaft seal is also not
- adapted for operation in contact with hydraulic fluid so that
the supporting member of the motor connected with the reduction
unit output shaft must also be filled with oil which is not
always warranted economically.
1~:198110
Qnother disadva~tage o~ said prior art l~eduction unit
lies in the necessity ~or additional devices intended to seal
of~ the cleaxa~ces b~t~leen the reduction gear d~iving and
d~iven shafts sotating at different speeds, and all the
splined jointr~ o~ the reduction unit shafts.
~h~ Known in the priox art is *se~dL reduction unit of a
dril].ing motor comprising an input shaft and an output ~ha~t,
both mounted on supports9 and a two-stage planetaxy reduction
geax accommodated in an oil-filled chamber. The channel for
Ç ~ v'l 1
the pas~ge of t~e d~illin~ ~liud i~ made in the form of a
circular space fitted arou~d the oil-filled chamber which
dispenses with the need for the seals between the driving
and driv~n sha~:ts of the reduction gear stages, rotating at
different speeds. The planet pinion~ of the planetary reduct-
io~ ~ear are installcd rotatably on tho ~ha~ts secured in the
pinion carricrs, the planet pinions of the seco~d stage being
a~ I o ,~ ~ ~ s
tw~ce ~se~th~n the planet pinions of the first atage.
A di~advantage of this reduction unit lies in that,like
in the above-described device, its employment i~ confined to
tbe drilling motors workin~ in conjunction with oil-filled
mechaniams because the reduction unit is devoid of the oil-
-protection system of its own. The use of this reduction
unit in hyd~aulic drillin~ motors is impossible.
~ nother disadvanta~e of said reduction unit lies in
that its input and output sha~ts aLo mad~ integral ~ith the
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p~rts of the reduction unit : the input shaft carries the
sun wheel at one end while the output shaft is made integral
w;th the 2nd stage pinion carrier, each shaft beiny mounted
on two rigi.d s~lr)ports. In this layout the parts of the unit
are complicated in rnanufactuxe; moreover, in case of wear of
the planetary reduction year parts i.t becomes necessary to
replace hoth the input and output shafts. Moreover, the working
conditi.ons of the gear drive are impaired hecause the elements
of the planetary reduction gear fail to be self-adjusted so
that the load is not distributed uniformly bet~een the planet
pinions. When the cantilever-mounted shafts of the reduction
unit are connected with the shafts of the adjacent sections, their
axial misalignment imposes heavy radial loads on the supports
of the input and output shafts thus ruining said sur)ports
prematurely.
One more disadvantaye of the prior art reduction unit
lies in that the planet pinion supports are located in their
inner holes which denies the possibility of changing their
load capacity because the planet pinions have but limited
radial dimensions. Apart from that, doubling the length of
2nd stage planet pinions of the reduction gear fails to ensure .
equal serviceability of both reduction gear stages because
the torque of the 2nd stage increase roughly proportionally
to the speed ratio of the 1st stage and said ratio for the
planetary transmissions used in the prior art reduction unit
is always higher than two.
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The ncarest technical solution is constituted by the
prior art reduction unit of a drilling engine comprising a casing
;nput and output shafts mounted on supports, a reduction gear
comprising sun and crown wheels, a planet carrier and planet
pir~ions with supports located in a circu]ar space between the
whee]s, an oil-filled chamber and a system of oil protection
collsisting of seals. The channel for the drilling fluid
has the form of a circular space fitted around the oil-filled
chamber on the outside.
A disadvantage of the prior art xeduction unit lies in
that its input and output shafts are mounted on rigid supports
installed at short distances from one another and that there
are long cantilevered porticns of said shafts which imposes
heavy radial loads on said supports and ruins them ultimately.
This causes play in the shafts and disturbs the tightness of
the seals.
Similarly to the above-described prior art reduction
unit the planet pinion supports are located inside said pinions-
and there are no devices protecting the reduction gear against
overloads and torque fluctuations.
Another disadvantage of the known reduction unit of a
drilling motor lies in that the seals are in contact with the
drilling fluid and are, therefore, rapidly worn so that the
`, oil-protection system loses its tightness.
One more disadvantage of the prior art reduction unit
lies in that its casing is made integral with the housing of
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~o~s~o
the working elements which prcvents the characteristics of
the drilling motor to be adjusted with the same working
e]ements by replacing a reduction unit by another one or by
consecutively connecting several reduction units for changing
the speed ratio of the reduction gear to suit the optimum
conditiolls of drilliny in each portion of the well.
The principal object of the present invention resides
in providing a reduction unit which will reduce the rotation
speed and increase the torque of hydraulic drilling motors.
Another object of the invention resides in extending
the service life of the reduction unit of a drilling motor.
One more object of the invention resides in raising
the load capacity of the reduction unit and its serviceabi]ity
under the conditions of fluctuating torque.
Moreover, an object of the invention resides in
si.mplifying the oil proection system of the reduction unit.
A further object of the invention resides also in
providing a reduction unit which would permit changing the
motor characteristics to obtain optimum drilling conditions.
These and other objects are accomplished by providing
a reduction unit of a drilling motor, comprising a casing,
input and output shafts mounted on supports, a reduction gear
including sun and crown wheels, pinion carriers and planet
;- pinions with supports located in a circular space between the
-~ wheels, an oil-filled chamber and a system of oil protection
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com~osed of seals incorporated wherein, according to the
invention, is a device safeguarding the reduction unit against
overloads and a tor~ue stabilizer eliminating the effect of
tor~ue fluctuations on the functioning of the reduction gear
and whcrei.n the supports of the input and output shafts
installed on the encls thereof connected with the reduction
year are made in the form of articulated units taking axial
loads and permitting angular displacement of the shafts, each
of said shafts being provided with a seal located side by side
with said support at the end opposite to ihe reduction gear,
said seal being provided with a dividing space filled with
a buffer fluid which protects said seal against contact with
the drilling fluid.
It is practicable that the overload safeguardshould
comprise inserts accommodating the planet pinion supports
installed in the slots of the pinion carrier and that part of
each slot mating with the insert should have the form of a
cylindrical surface whose axis is perpendicular to, and inter-
sects, the longitudinal axis of the reduction gear.
It is advantageous that the surface of the insert
.~ mating with the pinion carrier be barrel-shaped while the surface
located at the side of the pinion should be flat.
The inserts with the pinions are arranged in groups
wherein the distances between the axes of the adjacent pinions
within one group are shorter than the distances of the adjacent
pinions included into different groups.
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In one of the embodiments of the invention the
pinions are arranged at the minimum possible distances wi-thin
the groups.
It is expedient that the torque stabilizer eliminating
the effect of torque fluctuations on the performance of the
reduction gear be made in the form of a friction s~age of the
reduction gear, comprising a spring for compressing the
friction elements with a predetermined force.
It is practicable that the articulated units of the
input and output shafts be made in the form of spherical
bearings.
It is likewise advisable that the input and output
shafts be provided with additional supports connected with
the casing by flexible elements. There is a version wherein
the additional supports have the form of radial rubber-metal
sliding~contact bearings.
It is expedient that the dividing space be limited
by a seal, a tubular element connected to the casing, and a cover
secured on the shaft, the tubular element with the casing forming
a channel for the passage of the drilling fluid.
In one of the embodiments the dividing space has an
additional seal made in the form of an elastic diaphragm, the
portion of said diaphragm connected to the tubular element being
'~
located at the side of the seal while its opposite portion
;~ embraces the shaft for sealing it.
It is practicable that the density of the buffer fluid
; contained in the dividing space should be higher than that of
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the drill;ng fluid. In one of the embodiments it is suggested
to use a lubricating fluid in the function of the buffer fluid.
It is also practicable that the dividing space in the
reduction unit of the drilling motor should be in hydraulic
communication with the oil-filled chamber and that the latter
shouJd contain a buffer fluid.
The substance of the present invention consists in that
the devices for protecting the reduction gear against overloads
and torque fluctuations, the supports of the input and output
shafts in the form of articulated units, the arrangement of seals
side by side with the supports and the provision of dividing
spaces filled with a buffer fluid eliminate the adverse effect
of the well-drilling conditions on the reduction unit and ensure
its long service life.
The overload safeguard and the torque stabili%er allow
the reduction gear to be used under dlverse drilling conditions
which depend on a large variety of factors such as the bit
load, the moment capacity of the bit and rock, the rate of
flow of the drilling fluid through the working elements of the
motor, and the dynamic conditions at the well face. At a
limited diameter of the drilling motor and, as a consequence,
in absence of a considerable reserve in increasing the strength
of the main load-bearing elements of the reduction gear the
use of the above-listed means preserves the seriveability
of the reduction gear under heavy overloads and torque
fluctuations. However, sufficient durability of the reduction
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110
gear can be ensured only b~ operation in a ].ubricating fluid.
Making the supports of the input and output shafts
installed at the ends of said shafts connected to the reduction
gear in the form of articu],ated units which take axial loads
and permit ancJu],ar displacement of the shafts eliminates the
radial 1.oad$ on said supports when they are ax.i,a].ly misaligned
with the shafts of the working elements and of the support
assembly intended to convey the weight of the drill pipes on
to the bit. This ensures ]ong operation of the supports in
absence of radial and axial play. The installation of seals
on the shafts side by side with the suppor~s ensures but
insignificant radial vibrations of the shafts in the seals which
' remain sufficiently tight under these conditions while the
arrangement of the seals on the side of the shaft supports
opposite to the reduction gear enables the support to be placed
into the oil-filled chamber and thus to protect it agai.nst
. abrasive wear through contact with the drilling fluid. Thus,
the design of the supports in the form of spherical joints and
the arrangement of the seals relative to the supports according
to the invention creates the best conditions for the functioning
of both the seals and the supports of the input and output
shafts.
The life of the seals is extended still further because
each seal is provided with a dividing space filled with a
buffer fluid which protects said seal from contact with the
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drillin~ ~luid.
~ h~ location of the planet pinion supports in the inserts
in~talled in the slots of the pinion carrier makes it possible
to increase the size of thes~ s~pports, thereb~ raising their
load c~acity. The surfaces of' th~ carri~r slots mating with
the in~exts have a cylindrical shape and t~eir ~xes ax~
perpendicular to and intersect the longitudi~al axis of the
reduction gear, thus ensuring self-adjustment and u~iform
loading of the pinion supports in case of high torgues on the
pinion c~rrier. This layout of the reduction gear overload
afe~ua.rd impro~es the load distribution between the pinions
aljvst~
since it ensures self ad~iu~*~e~$ of two elements bf the pla-
netary tran~mission, i.e. sun wneel and planet pinions which
contributes to a longer li~e of the reduction gear txain. The
barr~l-shaped surface o~ the insert ensures self~-adjustment
of' the planet pinion supports in ca3e of' a cextain axial
mi~alignment betw~en the axis of the planet pinion and the
i r
lon~itudinal axis of the reduction gear ~ a radial plane.
~he flat surface o~ the insert at the planet pinion side
makes it pos~ible to reduce the length of the assemblg
including the planet pinion with supports and inserts and
thus to increase the load capacity of the reduction gear.
~ he arrangement of the inserts with plaDet pinions in
groups wherein the distances between the axes of the ad~acent
pla~et pinions within one group are shorter than the distances
bet~een the axes of the adjacent planet pinion~ included into
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different groups like~ise improves the load capacity o~ the
reduction gear and the rigidity of the pi~ion carrier because,
comparing with the uniform distribution o~ planet pinio~s in
the circular space, this layout increases the moment o~ inerti a
~d the moment of resistance of the pinion carrier in its sect-
io~ acro~ the slots. ~he ma~imum e~'~ect is obtained if the
ad~acent pla~et pinions within the groups are installed at
minimum possible axial distances.
~ he provision o~ the torque stabilizer in the form o~ a
friction stage of the reduction gear comprising a spring for
compressing tha friction elements with a predetermi~ed force
makes it possible to prevent the transmission of pea~ tor~ues
to the reduction gear elements due to momentary slipping of the
~riction elements o~ said friction stage.
~ he support~ of the input and output shafts o~ the reduction
unit made i~ th~ forM o~ spherical bearings en~ure ~imultaneous
tran~mission of the rotary motion of the sha~tæ and compen-
satio~ for the an~ula~ displacements o~ their axes.
Du~ to tbe arrangement wherein the additional supports o~
the input and output shaft are connected with the casing
through f'lexible elements it is possible to ensure the required
orientation of shaft axeæ during storage, transportation and
assembly o~ the drilling motors. Such supports may be made in
the form of radial rubber-metal sliding-contact supports.
Owing to the ~act that the dividing space is limited by a
seal~ tubular element and cover secured on the shaft and that
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the tubular elemen~ :orm~7 tegether with the casing, ~ cha~nel
for the passa~e of the drilling fluid~ the bu~`fer fluid is
preserved longex in the dividing space because the kine-tic e~ergy
of tbe fluid flow moving along the reduction u~it is suppressed
A by ~ cove~ and the fluid i~; dixected into .aid circular channel.
q'he additional seal made in t;he form of an elastic diaphra~m
connected at the side of the seal to the tubular element while
at the opposite side it embraces the shaft for sealing thereo~
during ~otation, rules out the mixing of the buffer and drilling
~luids.
~ he fact that the den~ity of the buffer ~luid filling the
dividing ~pace is higher than that of the drilling ~luid
prevents the so-called "floating" o~ the buffer fluid in the
drilling fluid and rules out the contact between the fluid
; a~d the seal when the space contains the buffer fluid.
~ he lubricatin~ material used as a buf~er fluid improve~
the durability of the ~eals; in addition~ penetration of tbe
buffer fluid into the oll-filled chamber does not shcrte~
the li~e of the reductio~ gear. ~his enables the dividing
space to be used as a container for stand-by lubricant which
makes up for the losses of the fluid from the oil-filled
c~amber, thereby dispensing ~ith one of the least reliable
units, i.e. lubricator. The use of the buffer fluid with
lubricating propertie~ permits hydraulic communication be-tween
the di~iding space and the oil-filled chamber, when the latter
~ it~
i5 filled wi~ the buffer fluid. ~his provides for maintainin~
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a constant pressure in the chamber on changes in the working
temperature, the hiyh density of the buffer fluid hinders the
penetration of the drilling fluid into the sealed units and
the design of the oil-protection system is greatly simplified.
In the reduction units of a drilliny motor realized
according to the invention ~he employment of the overload safe-
guard and torque stabilizer and the improvement of the oil-
protection system prolong the life of the unit under difficult
well-drilling conditions. The independent system of oil
protection and the casing of the reduction unit provide for its
effective employment with any type of the drilling motor. For
the practical purposes the present invention will be most useful
in the form of a set of reduction units with different speed
ratios which makes it possible to obtain any characteristic
of the motor with the same working tools and motor supporting
unit by changing or consecutively connecting several reduction
units directly in the borehole.
Now the invention will be described in detail by way of
example with reference to the accompanying drawings, in which:
Fig. 1 is a schematic longitudinal section of the
reduction unit of a drilling motor;
Fig. 2 shows an axial section through a planetary
reduction gear;
Fig. 3 is a section taken along line III - III in Fig.
2;
Fig. 4 is a section taken along line IV - IV in Fig. 3;
Fig. 5 is a section taken along line V - V in Fig. 2;
981~
Fig. 6 is a longitudinal section of a part of the
reduction unit with an embodiment of the dividing chamber;
Fig. 7 is a longitudinal section of one of the
embodiments of the reduction unit.
The reduction unit of a drilling motor, according to the
in~ention, comprises a hollow cylindrical casing 1 (Fig. 1)
connected with adapter sleeves 2 and 3 serving to fasten
the reduction unit elements in the casing 1. A reduction gear
4 consisting of sun and crown wheels, pinion carriers and planet
pinions with supports is accommodated in an oil-filled chamber A
formed by a cylindrical housing 5, by an input shaft 6 with a
seal 7 and an output shaft 8 with a seal 9. The reduction gear
is connected with the input 6 and output 8 shafts by gear
couplings 10. The articulated supports of the shafts 6 and 8
are made in the form of spherical roller bearings 11. The seals
7 and 9 are provided with dividing spaces B and C, respectively,
filled with a buffer fluid which protects the seals from contact
with the drilling fluid. The space B is limited by the seal 7,
bushing 12, fixed immovably on the shaft 6, a tubular element 13
tightly secured to the housing 5 and located above the seal 7,
and by a cover 14 installed above the tubular element 13 and
secured on the shaft 6 by means of bushings 12, 15, 16 and coupling
member 17 screwed on the threaded end of the shaft 6.
The dividing space C also comprises tubular elements 18
and 19 connected with the housing 5, and a cover 20 secured
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1~9~
on the shaft 8 by bushings 21 and 22 with the aid of coupling
member 23 screwed on the threaded end of the shaft 8. The buffer
fluid contained in the spaces B and C is selected in order to
5atisfy the requlrement of good adhesion to metal and absence
of the tendency towards formation of chemical and mechanical
compourlds with the components of the drilling fluid. The buffer
fluids are usually selccted to have a density higher than that
of the drilling fluid and to be lubricious in operation. The
channel D intended for the passage of the drilling fluid is
made in the form of a circular space between the casing 1 and
associated bushings 24 and 25 at one side and the housing 5
and associated tubular elements 13 and 18 at the other.
The reduction unit is installed in the drilling motor
in such a way that the adapter sleeve 2 is connected to the
casing of the working tools while the adapter sleeve 3, to
the casing of the motor supporting unit. Correspondingly, the
shaft 6 is connected by the coupling member 17 with the driving
shaft of the motor with a provision for transmitting torque
while the shaft 8 is connected by the coupling member 23 in the
same manner with the shaft of the motor supporting unit. Such
a connection of the shafts permits relative axial displacement
of the couplings without applying considerable axial forces
to the spherical bearings 11; at the same time these connections
play the role of additional supports for the shafts 6 and 8.
During operation of the drilling motor the shaft 6
is driven from the motor driving shaft; then rotation is further
transmitted by the gear coupling 10 to the drive shaft of the
reduction gear wherein the rotation speed is reduced with a
corresponding increase of torque. Now rotation with
1(~9~
new parameters is transmitted by the second gear coupling lO
to the output shaft 8 and further, via the coupling member 23
and the shaft of the supporting unit, to the rock-breaking
tool (bit). Axial misalignment of the shafts 6 and 8 relative
to thc associated shafts of the adjacent units is made up for
by the angular displacements of the axes of the reduction unit
shafts 6 and 8 without applying radial forces to the supports
due to the use of spherical supports 11. Thanks to the fact
that the seals 7 and 9 are located near the supports 11, even
the maximum possible range of angular displacements of the axes
of the shafts 6 and 8 their radial play in the seals is very
small (up to 0.2 mm) which is permissible for normal functioning
of the seals utilized in the drilling motors. The absence
of axial play in the supports ll and an insignificant range of
radial vibrations of the shafts 6 and 8 at the point of the
seal ensure good conditions for long functioning of the seals
which, in its turn, contributes to longer life of the supports ll
on the condition that lubrica~t is preserved for a long time in
chamber A.
2Q The dividing spaces B and C filled with buffer fluids
rule out the contact of the seals 7 and 9 with the drilling
fluid containing abrasive particles; besides, washing out of
lubricant from the spaces by the drilling fluid is hindered due
to the difference in the densities and other properties of
the fluids mentioned before. The cover 14 protects the
buffer fluid in the space against being washed out by the
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velocity head of the drilling fluid by reducing its kinetic
energy and directing the flow into the circular channel D.
When a suffici.ently large amount of buffer flui.d is accumulated
in the space B the l,atter can a].so function as a device
(lubrica-tor) intended to make up for the losses of lubricant
from ~he chamber A. The leaks occur mostly in the lower seal
9 because the drilling fluid loses a part of pressure in the
channel D while pressure inside the oil-fil~,ed chamber A
stays approximately constant which makes for the pressure
differential on said seal at the side of the chamber A. The
leaks decrease pressure in chamber A which is accompanied
by a smaller pressure drop on the seal 9 and a larger pressure
drop on the seal 7, said pressure drop being directed from the
space B into the chamber A. Under the effect of this pressure
~rop the lubricious buffer fluid penetrates into the chamber A,
compensating for the oil leaks. The buffer fluid may consist
of thickened and heavy oils, consistent lubricants, plastic
materials, and liquid metals and alloys. The buffer fluid must
be selected so that its mixing with the lubricating material
contained in the chamber A would not reduce the lubricating
properties of both liquids. To replenish the reserve of
lubricants in the chamber A and spaces B and C, the casing 1
has holes for valves and plugs (not shown in the drawings).
To improve orientation of the shafts 6 and 8 when the
reduction units are transported in a horizontal position, also
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when they are ;nstalled in the drilling motor it is good
practice to provide said shafts with special radial supports
connected wi,th the casing 1 by flexible elements which reduce
the radial ~oading of the supports in case of axial misalignment
of the shafts being connocted. In Fig. 1 said supports are shown
in the form of rubber-metal radial sliding-contact bearings 26
with bushings 27 wherein the flexible elements are formed by
rubber covering of the bearing 26.
The planetary reduction gear of the unit may have
different designs and speed ratios depending on the requirements
of efficiency of the drilling work. A version of the reduction
gear 4 is shown in Fig. 2. It comprises the stages of the
planetary gear train including sun wheels 28 and 29, crown
wheels 30 and 31, planet pinions 33, 33 with supports 34, and
pinion carriers 35 and 36. The gear stages are interconnected
by torque-transmitting couplings 37 which can be either splined
or gear type. The driving shaft 38 of the transmission is
connected with the input shaft 6 via the coupling member 39 and
coupling 10 (Fig. 1) while the driven shaft of the reduction
gear - pinion carrier 36 - is connected by the coupling 10
with the output shaft 8. The 1st friction stage of the reduction
gear is made to function as a torque stabilizer, i.e,, a device
eliminating the effect of torque fluctuations on the operation
of the entire reduction gear. This is achieved by providing
the friction stage with a spring 40 mounted on a shaft 38 and
pressing the bevel sun wheels 28 against the tapered surfaces
of the planet pinions
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32 which, in turn, are pressed by the cylindrical surfaces
against the crown wheel 30 connected with the reduction unit
casing 1. The parameters of the spring 40 are such that the
cornpression of the friction elements 28, 32, 30 ensures trans-
rnission of a maxiltlum torque required for normal operation of
the rock-breaking tool. When this torque starts fluctuating
and l~s upsurges may ruin the reduction year elements, the
friction elements of -the stage slip momentarily thus reducing
the torque upsurge.
The 2nd toothed stage of the reduction gear incorporates
an overload safeguard. It includes inserts 41 (Figs. 3,4) with
the supports 34 of the planet pinions 33 which are installed
in the slots E of the pinion carrier 36. The portion El of each
slot E mating with the insert 41 has the form of a cylindrical
surface whose axis is perpendicular to the longitudinal axis of
the reduction gear (coinciding with the axis of the sun wheel 29)
and intersects it. The surface F of the insert 41 mating with
the cylindrical surface of the slot E is barrel-shaped (Fig. 4).
The surface G of the insert 41 (Fig. 3) facing the planet
pinion 33 is flat. The planetpinions 33 with supports 34
and inserts 41 are located in the circular space between the
sun wheel 29 ana the crown wheel 31 irregularly, in groups (Fig. 5)
so that the distances between ~he axes of the adjacent planet
pinions 33a and 33b within one group are shorter than the
distances between the
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axes of the adjacent planet pinions 33b and 33c included in-to
difFerent groups. Accordingly, the cross sectional aréas and
thc moments of resistance of the pinion carrier elements 36a
and 36b ~re different too.
All the above-mentioned d;stinguishing feal-ures of the
toothed stage of the reduction gear are aimed at raising the
load capacity of the wearest reduction gear elements such as
supports 34, planet pinions 33 and pinion carrier 36. Thus,
their load capacity rises sufficiently for transmitting the
torque ensuring normal functioning of the drilling bit. When
torque is transmitted via the reduction gear 4, its pinion
carrier 36 is twisted relative to the longitudinal axis, the
carrier elements 36a and 36b (Fig. 5) bend with respect to
axes X - X and Y - Y which is accompanied by turning of the
shafts of the planet pinions 33 (Fig. 3) through a certain angle.
The arrangement of the reduction gear 4 in accordance with
the present invention raises the total moment of resistance of
the carrier elements 36a and 36b in comparison with the
reduction gear whose planet pinions are spaced regularly and
uniformly in the circular spacè. The maximum effect is achieved
when the planet pinions 33a and 33b are contiguous to each other
(Fig. 5), i.e., when the axis-to-axis distances of the planet
pinions 33a and 33b are minimum and meet all the requirements
of assembling the planetary transmission. The stresses in said
elements of the pinion carrier are reduced still more because
a considerable radius R (Fig. 3) of the cylindrical surface
practically excludes stress
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concentrations at the junctions between the longitudinal 36a
and transverse 36c elements of the pinion carrier. The flat
shape of ~he surfaces G makes it possible to reduce the total
Lenyth of the s]ot E 2 which contributes to higher strength
and stiffness of the pinion carrier. At the same time,
installation of the planet pinion supports 34 in the inserts
41 permits increasing their diameters and longitudinal loading
as compared with the versions in which the supports are located
inside the planet pinions. The operating conditions of the
supports 34 are made still better due to the barrel-like
shape of the insert 41 which permits the supports 34 to be
self-adjusted if the shaft of the planet pinions 33 is mis-
aligned in two mutually perpendicular planes.
A version of the dividing space B (Fig. 6) incorporates
an auxiliary seal in the form of an elastic diaphraym 42.
One side of the diaphragm 42 is reinforced by metal rings 43
which allows the diaphragm 42 to be press-fitted into the
tubular element 13. At the other side the diaphragm fits around
the bushing 12 secured on the shaft 6 with an interference
of 5 - 7 mm for sealing said bushing but permitting the shaft
6 to rotate together with said bushing 12. This auxiliary seal
divides the space B into two parts sl and B2. The space Bl
accommodates a lubricating buffer fluid while the buffer fluid
in the space B2 is gradually substituted by the drilling fluid.
As the fluid gradually escapes from
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the chamber A the lubricant is replenished from the space Bl.
An advantage of this version lies in a longer preservation of
the buffer f]uid in the space s.
The version of the reduction unit of a drilling motor
(J~'ig. 7) diffcrs from the basic version (Fig. 1) in that the
dividing space B communicatcs hydraulically through channel
L with the oil-filled chamber A which accommodates the reduction
gear 4 and supports 11 : the chamber A, like the chamber
B, is filled with a lubricious buffer fluid. In such an arrange-
ment the pressure of the drilling fluid is conveyed from thespace B into the chamber A through channel L. When the fluid
volume changes in the chamber A due to thermal variations
and the fluid flows back and forth through channel L, pressure
in said cham~er remains unchanged so that the seal 7 is practically
free from the effect of pressure drop. Its functions consist
only in preventing the settling solid particles from entering
the chamber A when the fluid located in the upper part of the
space B above the buffer fluid is not cleaned sufficiently
well. Therefore, the design of the seal 7 is simpler than it
2C is in the basic version (Fig. 1). For example it has the
form of an edge-type labyrinth gate. The reduction unit of a
drilling motor according to this layout (Fig. 7~ is extremely
simple, sufficiently reliable and durable.
The use of the above-described technical solutions
has made it possible to work out a simple and dependable design
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of the EedUCtion l~it of a drilling motor ~hich allows-
e~icient drilling of wells with variou~ type~ o~ drilling
motors, practically at any depth attai~able today with the
c:urrent hydraulic eguipment o~ the drilling rigs. ~e self-
~suf~iciency o~ the unit and its oil protect:ion system permit
its use in the form of a.set of several reduction unit~
ensuriDg a series of speed ratios capable o~ providing a wide
range of performance characteristics required by diverse
drilling conditions without changing the ~orking elements and
motor supporting units. Said units can be ~urnished to the
drilling rig in a set while the re~uired characteristic o~
the motor can be determined directly at the borehole by replac-
ing or consecutivelg combining several rednction units.
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