Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Background of the Invention
This invention relates to wall contacting tools
useful in earth boring, especially by the rotary system, and
more particularly to a fixed blade, rotating stabilizer whose
wall contacting elements are in the form of replaceable wear
pads~
In United States patent number -
3,680,647 ~ Dixon & Crewsthere is disclosed a wall contacting tool, specifically a
fixed blade stabilizer, having replaceable wear pads of
approximately sector shape cross section. The corner of each
pad is received in a correlative V groove flute in the outer
periphery of an arm of the tubular body of the stabilizer.
The pad corner and flute apex angle is ninety degrees. The
pad is secured to the body by a plurality of cap screws
extending laterally throuah the pad into the two sides of the
flute. Various prior Unlted States patents referred to in
the patent are numbered:
3,454,308 - ~ennedy
2,084,421 - Wright
2,973,996 - Self
3,292,708 - ~Iundt
2,088,770 - Skinner
2,589,534 - Buttolph.
The Kennedy, Wright and Self patents show various forms of
wall contacting tools with wall contacting elements secured
to the body by radially extending screws. Various and other
forms of retention are shown in the Skinner, Mundt and Buttolph
patents. Reference also may be made to United States patents
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3,326,305 - Garrett
3,545,825 - Hamilton
which are referred to in United States patent number
3,818,999 - Garrett.
In United States patent
3,818,999 - Garrett
there is disclosed a stabilizer having wear pads of generally
sector shape cross section, each disposed in a correlative
90 angle V groove or flute in the stabilizer body. Each pad
is held in place by dowel pins in the apex of the wear pad
corner and body flute, the dowel plns preventing lateral
movement of the pad. Each dowel pin has a head anchoring it
to the body. Each dowel pin has a screw receiving soc~et and
thus constitutes a nut, such nut receives a cap screw extend-
ing ~hrough a stepped bore in the pads to hold the pad to the
body. Because there are a plurality of dowel pin-nuts for
each wear pad, the dowel pin function of the dowel pin-nuts
is less effective. This is by reason of the sloppy fit
between the dowel pin-nuts and the bores of the pads and body
in which they are received, as required to insure that the
parts will fit together when made to reasonable tolerances.
Because of the sloppy fit, shear loads are not confined to
the dowel pin-nuts; the shear loads are transferred in large
measure to the cap screws.
For the foregoing reason and perhaps others, the
assembly can be loosened in use by excessive force, e.g. in
directions parallel to the stabilizer aY.is (hereinafter
referred to as axial force) caused, e.g. by the stabilizer,
during a trip, passing through a tight place in the earth
bore, causing the cap screws to be stretched beyond their
elastic limit, or by excessive torque on the wear pads, due,
e.g. to turning in a tight bore or while heavily pressed
laterally against the side of the well bore, causing the cap
screws to be stretched beyond their elastic limit, or by
excessive vibration during rotation in the bore, causing the
cap screws to turn relative to their nuts and work loose, or
by normal vibration causing improperly tightened cap screws
to come loose, or by obstructing material such as dirt or
metal burrs at the mating surfaces of the assembly disappear-
ing or reducing in size under the repeated stresses occurring
when the stabilizer is in use, thus loosening the cap screws
When the assembly is loose, the cap screws may fall
out, the loose pad may break and fall off, the dowel pin-nuts
may drop out, and the stabilizer body may be da~aged by the
movement of the loose pad relative to the body.
It is the object of the invention to overcome the
aforementioned difficulties. It has heretofore been sug-
gested that a retainer ring might be placed over the head of
each cap screw, disposed in a groove in the wear pad. How-
ever, this does not prevent the cap screws from turning, for
the wear pad can move with the cap screws away from the
stabilizer body as the cap screws turn in the dowel pin-nuts.
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Summary of the Invention:
According to the invention the assembly comprising
the stabilizer body, cap screws and radial dowel pin-nuts,
described in the aforementioned Garrett patent, is provided
b~th with retainer rings set in the wear pads over the heads
of the cap screws and with a lateral dowel pin extending
between one side of each wear pad and the adjacent side of
the V groove in the stabilizer body in which the pad is
mounted. This is possible by virtue of the V groove having
substantially a ninety degree apex angle. With the un-
dowelled side of a pad bearing against the correlative side
of the V groove, the pad can be assembled to the body by
sliding side ways into position. The lateral dowel pin
registers with the socket in the other side of the pad or the
other side of the V groove, the dowel pin having been ini-
tially inserted in a socket in either the pad or the body.
After each pad is slid into position to engage the dowel pin
in its side, the cap screws are scre~ed into the dowel pin-
nuts in the apices of the pad and V groove and the retainer
rings are installed over the heads of the cap screws.
It will be seen that the foregoing arrangement
prevents the cap screws from coming out of the assembly, even
if loosened, since the lateral dowel pin in each pad prevents
relative movement of the pad and body in the direction of the
cap screw axes and the retainer rings prevent relative axial
movement of the cap screws and pad. According to the inven-
tion there is thus provided a positive lock retaining the
wear pad to the body of the stabilizer. The lateral dowel
pin also provides additional strength to the assembly in
resisting axial forces and torque imposed on the pads. If,
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as is preferable, only one lateral dowel pin is used per pad, it can be
made to have a tight fit with its s.ockets, since it ;s unnecessary to
maintain any dowel pin separation (spac;ng) dimens;on, there being only
one lateral pin per pad.
According to one aspect of the invention, there is provided a
wall contacting tool comprising a body and a wear pad, said body and pad
having correlative flute and corner means extending along the body prevent-
ing relative.motion of pad and body transverse to the length of said means
except motion outwardly from the apex of the corner, screw means extending
through the pad into a screw socket carried by the body to prevent
relative motion of pad and body outwardly from the apex of the corner,
the axis of said screw means bisecting the apex angle of the corner and
flute, said apex angle being ninety degrees, releasable retention means
preventing relative motion of said screw means and pad along the bisector
of said apex angle, and dowel means extending between one side of said
flute means and the adjacent side of said corner means, said dowel means
preventing relative motion of said pad and body parallel to the length of
said flute and corner means and further preventing relative motion of said
pad and body outwardly from the apex of said flute and corner means.
According to another aspect of the invention, there is provided a
drill string stabilizer comprising a tubular body having a plurality of
longitudinally extending arms, each arm having a flute extending longitudi-
nally thereof at its outer periphery, the sides of each flute being planar
and disposed perpendicularly to each other with the plane bisecting the
angle between the sides of the flute being radially disposed relative to the
axis of the tubular body of the stabilizer, a plurality of dowel pin sockets
in each arm along the length of each flute each disposed with the socket axis
bisecting the angle between the sides of the flute and radially relative to
the axis of the tubular body of the stabilizer, a pair of bayonet slots
extending from each dowel pin socket, a radial dowel pin having a pair of
lugs ada.pted to be received in said bayonet slots and turned into position
preventing withdrawal from the socket, each radial dowel pin having a
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threaded bore, a plurality of wear pads, each pad having two planar sides
disposed perpendicularly to each other and a cylindric outer face there-
between extending the length of the pad, a plurality of said pads being
disposed end to end in each flute, a plurality of stepped bores in each
pad in register with said dowel pins, a cap screw in each stepped bore with
its threaded stem screwed into the threaded bore of the respective radial dowel
pin and having its head bearing against the step in the bore, an annular
groove in each stepped bore just outwardly from the cap screw head, a retainer
ring in each said annular groove, a pair of registering sockets in one side of
each pad and the adjacent side of the respective flute, and a lateral dowel
pin in each said pair of sockets extending from one of said pair of sockets
into the other of said pair of sockets preventing longitudinal movement of
the respective pad relative to the arm and preventing radial outward move-
ment of the pad relative to the arm, whereby said cap screws cannot come
unscrewed from said radial dowel pins.
According to a further aspect of the invention, there is provided
a wall contacting tool for use in rotary drilling comprising: a tubular
body and a replaceable external wear pad secured thereto by screw means
extending transverse to the axis of the body and threaded aperture means
receiving said screw means and connected to the body against rotation of the
threaded aperture means relative to the body about the axis of the threaded
aperture means, and means to prevent said screw means from unscrewing from
said threaded aperture means comprising:
(1) releasable retainer means to prevent the screw means from moving
axially relative to the pad, and
(2) anchor means to prevent relative tion in the direction of the axis of
the screw means between the pad and said threaded aperture means connected
to the body, whereby upon loosening of said screw means complete release
of said screw means from said threaded aperture means is prevented.
According to yet another aspect of the invention, there is provided
in a replaceable wear pad for use with a wall contacting tool, such tool
comprising a body having a Vee cross-section flute with an apex angle of
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at least ninety degrees whose bisector is radial to the tool axis, said pad
having a Vee cross-section providing a corner adapted to fit in such a flute~
said pad having a stepped bore bisecting the apex angle of the corner of the
pad adapted to receive a cap screw to extend radially of the tool axis for
securing the pad to the body with the head of the cap screw bearing against
the step of said bore and engaging a threaded aperture in said flute
connected to said body against rotation relative to the axis of said threaded
aperture, the improvement in means for preventing said screw from unscrewing
from said threaded aperture comprising:
(1) the larger diameter portion of the stepped bore having an annular groove
about its inner periphery adapted to receive a resilient ring to retain such
screw in such bore, and
(2) at least one socket in one side of the corner of said pad adapted to
receive a dowel pin to traverse the interface of said one side of the pad
and an adjacent side of the flute of such body to prevent motion of said pad
relative to said threaded aperture connected to said body in the direction ^`
of the axis of said bore, said socket having an axis transverse to the
plane of the bisector of said apex angle of said corner whereby upon
assembly of said pad to said body the axis of said bore will be non-radial
relative to the axis of the tool, and whereby upon loosening of said screw
complete release of the screw from said threaded aperture will be prevented.
Brief Description of the Drawing
For a more detailed description of a preferred embodiment of the
invention, reference will now be made to the accompanying drawings wherein
FIGURE 1 is an elevation of a stabilizer embodying the invention;
FIGURE 2 is a section taken at planes 2-2 of FIGURE l;
FIGURE 3 is a fragmentary elevation viewed from plane 3-3 of FIGURE
2, partly in section;
FIGURE 4 is a fragmentary section taken on planes 4~4 of FIGURE 2;
FIGURES 5 and 6 are respectively side and front views of a dowel
pin-nut used in the stabilizer;
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FIGURES 7 and 8 are respectively front and side views of a
retainer ring used in the stabilizer; and
FIGURES 9 and 10 are side and end views of a lateral dowel
pin used in the stabilizer.
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Description of Preferred Embodiment:
Referring now to Figure 1 there is shown a stabi-
lizer comprising a tubular body ll having a threaded tool
jolnt box 13 at its upper end for making connection to a
portion of a drill string thereabove and a tool joint box 15
at its lower end for making connection with a drill bit.
The tool could be modified by putting other types of connec-
tors at its ends, e.g. to adapt the stabilizer for use higher
up in the drill string, a tool joint pin could be put at the
lower end of the tool, providing means for making connection
with a portion of the drill string thereabove. The body has
an axial flow passage 17 extending from end to end thereof.
The body is provided with a plurality, e.g. four,
as shown, of longitudinally extending ribs or arms or blades,
equiazimuthally spaced apart about the axis of the body. The
channels 21 formed between the arms provide axial flow pas-
sages over the exterior of the body.
Releasably secured to each arm are a plurality of
wear pads 23. If desired, the upper and lower ends of the
ribs can be protected by wear pads welded thereto; this is
shown in the published description of the commercial e~oodi-
ment of the previously known stabilizer upon which the pre-
sent sta~ilizer is an improvement. Such description appears
at pages 21a2-2144 of the 1976-77 edition of the Composite
Catalog of Oil Field Equipment & Services copyright 1976 by
Gulf Publishing Company, to which reference may be made for
further details. However such supplemental pads are not
essential; see the leaflet entitled "Drilco's Replaceable
Wear Pad Stabilizer" published by applicant's assignee, copy
enclosed with this application.
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Each pad 23 is held in place by means including at least one cap
screw 25, three per pad being shown ïn FIGURE 1.
Referring now To FIGURES 2-4, each pad 23 is an elongated
member or bar having a generally sector shape cross section forming
a corner 26 having sides 27, 29 disposed substantially perpendicularly
to each other, which if projected to their intersection form an apex
angle of substantially nïnety degrees. However, the actual point of
the corner is rounded. The cylindric face 31 of each pad is concentric
with the axis 33 of flow passage 17 rather than being centered at the
apex of corner 26; for this reason the cross section is described as
"generally" sector shaped.
Referring again to FIGURE 1, as well as FIGURES 2 and 3, the
face of each pad is provided with a plurality of tungsten carbide
compacts 35 pressed into sockets in the pad. Any other ~orm of wear
resisting means may be employed for the face of the pad, e.g. as shown
in the aforementioned Garrett patent number 3,818,999, or the pad may
merely be made of hard metal or even left unprotected so as to ablate in
use. It is to be understood that except for the inserts, all parts of
the disclosed stabilizer are preferably made of steel.
Each arm 21 is provided with a longitudinally extending V
groove or flute 37 having sides 39, 41 disposed substantially
perpendicularly to each other, which, if projected to their inter-
section form an apex angle of substantially ninety degrees. However,
the actual bottom of each groove is rounded, but not as much in the
corner of each pad, so that when a pad is positioned on an arm, the
point of the corner of the pad does not touch the bottom of the groove.
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To prevent longitudinal motion of each pad relative
to the body, each arm is provided with a plurality of generally
cylindrical radial soc~ets 43 in register with a plurality of
generally cylindrical radial sockets 45 in the corners of the
pad. In each registering pair of sockets 43, 45 is disposed
a radial dowel pin 47. Each radial dowel pin 47 has a pair
of lugs 49, 51 received initially in vertical slots 53, 55
adjacent soc~et 43 and then, after the dowel pin has been ~
turned 90, disposed in slots 57, 59. The lugs hold the
radial dowel pin against radial outward movement. ~he por-
tions 61, 63 of the pad corner above and below each socket 5
in the pad enter the slots 53, 55 in the arm and prevent the
radial dowel pin from turning.
Each radial dowel pin has a threaded bore 65 re-
ceiving the threaded stem 67 of one of the cap screws 25.
Radial dowel pins 47 may therefore be called dowel pin-nuts.
Each cap screw stem 67 extends through the small diameter
portion 69 of a stepped bore 71 in the face of the pad. Cap
screw head 73 bears against the step formed at the juncture
of the large and small diameter portions of the bore so that
when the screw is tightened it draws the pad radially toward
the body. Preferably the tolerances are set so that the apex
angle of each pad corner is al~ays slightly greater than the
apex angle of the flute, and reliance is placed on the cap
screws to bring the sides of e2ch pad corner into engagement
with the receptive flute.
Each cap screw is secured against radial outward
motion by a retainer ring 75 received in an annular groove 77
in the large diameter part of stepped bore 71. As best shown
in FIGURE 6, each ring 75 is split at one side and provided wit~
. . . ~ . .
a pair of openings or eyes in the ends 78, 79 of the ring to receive a
tool for drawing the ends of the ring together so the ring diameter
will be small enough to allow insertion through bore 71 to a position
adjacent groove 77 ~see Figure 2). The resilience of the ring is
such that upon release of the tool the ring springs into groove 77.
The ring is wider than the depth of the groove so that the inner
periphery of the ring extends over the head of the cap screw and
prevents it from coming out of the pad.
Referring now particularly to FIGURE 4, as well as the other
figures, in the lower part of side 41 of each flute, between the levels of
the middle and lowermost radial dowel pins there is a cylindrical socket
81 in which is disposed a lateral cylindrical dowel pin 83. In the
lower part of side 29 of each pad is a cylindrical socket 85 adapted to
receive the portion of lateral dowel pin 83 that protrudes from socket 81
in the side of the flute. Since the sides of the flute are substantially
perpendicular, as are the sides of the corner of the wear pad, one side of
the pad can be slid along one side of the flute until the other side of
the pad engages the other side of the flute, and the lateral dowel pin in
such other side of the flute will be in register with and enter the
socket in such other side of the pad.
If desired the lateral dowel pin can initially be placed in the
pad and enter the socket in the side of the flute as the pad is slid into
position. The lateral dowel pin makes a close fit with its sockets in
the pad and body so as to take shear loads and thereby supplement the
radial dowel pins. Because the latter do not make such close fits with
their socketsJ due to tolerances required in manufacturing, the one
lateral shear pin may take as much load as
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the three radial dowel pins combined. It will be understood
that the closest fitting dowel pin, which is the lateral pin,
will usually have to be strained somewhat before one of the
radial dowel pins will even begin to take shear load.
Nevertheless, each lateral dowel pin makes a loose
enough fit with its sockets such that it can be removed by
hand, or pulled out with a pair of pliers. In other words,
the fit is a close fit but preferably not an interference
fit.
Each pad is assembled to the body by first insert-
ing the radial dowel pin-nuts into the body and turning them
so the lugs are perpendicular to the body axis. Then the
pads are slid into position with the lateral dowel pins in
engagement with their sockets. Next the cap screws are
screwed into the radial dowel pin-nuts and tightened. Finally,
the retainer rings are installed over the cap screws. The
reverse procedure is followed when a pad is to be removed for
replacement. At the same time other parts, such as lateral
dowel pins, radial dowel pin-nuts, cap screws, and retainer
rings, if worn out, may be replaced.
As long as the retainer rings are in position, the
cap screws cannot come out of the pads and the lateral dowel
pins prevent the pads from coming out of the flutes, so that
the assembly is positively locked together.
One of the advantages of the invention,
in addition to those previosuly set forth, is that
t]ie pads are positively retained in place on the
stabilizer arms even if the heads of the cap screws
break off. The retainer rings keep the heads in the
pad and the heads prevent the cap screw stems from
moving axially in the pads. Since the pads are held
to thearms by the lateral dowel pins, the cap screw
stems cannot unscrew from the dowel pin-nuts and the
assembly stays together. When it comes time to replace
the pad, the cap screw stem can be removed by horing a
hole in its and removing the stem with a backout tap.
Preferably, an overshot type tool comprising a helical
wire spring suitably mounted on a Tee shaped handle
is employed to remove such broken cap screw stems.
The coil can be screwed onto the reduced diameter
unthreaded part of the cap screw stem and then turned
oppositely to tighten it on the cap screw stem and finally
to unscrew the stem from the dowel pin-nut. If the cap
screws have right hand threads, the removal tool spring
will be a left hand helix.
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S~rizing, there is provided a stabilizer
having three or more arms, each with a wear pad
extending longitudinally at the outer end of the
arm. Each pad is secured to an arm by flute and
corner means comprising a ninety degree corner on
the pad received in a 90 flute in the arm, radial
dowel pins bisecting the ninety degree angles of the
flute and corner and extending radially relative to the
flow axis of the tubular ~ody of the-stabilizer,
bayonet joint means releasably holding each dowel
pin to the body comprising lugs on the dowel pin
entering slots in the body and then turned into recesses
at each side of the slots, cap screws passing through stepped
bores in the pads into l~readed sockets in the radial
dowel pins, releasable resilient, split retainer rings
received in annular grooves in the stepped bores to
overlie the cap screws, and a lateral dowel pin across
the interface between one side of each pad corner and arm
flute, the lateral dowel pin extending perpendicularly
from a side of the`-flute into a registering socket in
the corner of the pad, both sockets having axes perpen-
dicular to the interface.
While a preferred embodiment of the invention
has been shown and described, modifications can be made
by one skilled in the art wi'.nout.departing from the
spirit of the invention.
