POLISH ROD LOCKING CLAMP

ATTACHE VERROUILLABLE D'UNE TIGE POLIE

English Abstract

A polished rod lock out clamp for use in securing the polished rod in an oil well installation, comprising a clamp body having a bore for receiving a polished rod in spaced relation to the bore; clamp members in the clamp body for engaging a polished rod in the bore; and radial bolts secured to the clamp body and the clamp members for moving the clamp members between a polished rod gripping position where the clamp members grippingly engage the polished rod to prevent rotation and axial movement thereof and a retracted position where the clamp members are removed from the polished rod to permit rotational and axial movement of the polished rod in the bore of the clamp body.

French Abstract

Un collier de serrage pour le verrouillage d'une tige polie est proposé, ledit collier de serrage étant destiné à être utilisé dans la fixation de la tige polie dans une installation de puits de pétrole. Ledit collier de serrage comprend un corps de collier de serrage qui comporte un alésage pour recevoir une tige polie en relation espacée par rapport à l'alésage ; des éléments de collier de serrage dans le corps de collier de serrage pour entrer en prise avec une tige polie dans l'alésage ; et des boulons radiaux fixés au corps de collier de serrage et aux éléments de collier de serrage pour déplacer les éléments de collier de serrage entre une position de préhension de tige polie, dans laquelle les éléments de collier de serrage entrent en prise par préhension avec la tige polie pour empêcher la rotation et le mouvement axial de celle-ci, et une position rétractée, dans laquelle les éléments de collier de serrage sont retirés de la tige polie pour permettre les mouvements de rotation et axial de la tige polie dans l'alésage du corps de collier de serrage.

Claims

WE CLAIM:


1. A polished rod lock out clamp operable to suspend a polished rod in an oil
well
installation, comprising:
a clamp body having a bore for receiving the polished rod therethrough in
spaced
relation to said bore;
clamp members in said clamp body for gripping the polished rod in said bore;
and
manipulating means secured to said clamp body and said clamp members for
moving
said clamp members between a polished rod gripping position in which said
clamp members
grippingly engage said polished rod in metal to metal contact therebetween to
prevent
rotation or axial movement of the polished rod, and a retracted position in
which said clamp
members are removed from the polished rod to permit rotational and axial
movement of the
polished rod in said bore of said clamp body.


2. A clamp as defined in claim 1, each said clamp member being radially
movable with
respect to said polished rod and having an arcuate inner surface for engaging
said polished
rod thereinto.


3. A clamp as defined in claim 2, wherein the diameter of said inner surface
is slightly
less than the diameter of the polished rod to enhance gripping force.


4. A clamp as defined in claims 1, 2 or 3, wherein each said clamp member is
in the
form of a piston, said clamp body having a piston bore for each said piston,
each said piston
bore extending radially of said bore of said clamp body, each said piston
having an inner end
proximate said bore of said clamp body, said arcuate inner surface being
formed in said inner
end to be semi-circular in shape for receiving and grippingly engaging said
polished rod.

5. A clamp as defined in claim 4, comprising a pair of said pistons radially
opposed to
one another.


6. A clamp as defined in claim 5, said pistons having mutually engageable end
faces
at said inner ends thereof and seal means disposed between said end faces,
said pistons
being sealingly disposed in said piston bores and being sealingly engageable
with said
polished rod and with each other to prevent well fluids from escaping past
said clamp when
said pistons are disposed in said gripping positions thereof.



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7. A clamp as defined in claims 2 or 3, said clamp members comprising a pair
of
opposed clamp members each forming an elongated segment of a cylinder and each
having
a said arcuate inner surface for engagement with the polished rod.


8. A clamp as defined an any of claims 1 to 7 including resilient members
disposed
between said clamp members to normally bias said clamp members towards said
retracted
position thereof.


9. A clamp as defined in any of claims 1 to 8, said manipulating means
including, for
each clamp member, a bolt threaded into said clamp body for moving said clamp
member
between said gripping and retracted positions thereof.


10. The clamp as defined in claim 9, wherein each said bolt includes a shaped
portion
formed on an inner end thereof for mating engagement with a correspondingly
shaped slot
in a respective clamp member for moving said members into said retracted
position thereof.

11. A clamp as defined in any of claims 1 to 10, wherein said clamp is
arranged to be
secured between a polished rod drive head and a well head of the oil well
installation.


12. A clamp as defined in any of claims 1 to 11, wherein said clamp forms part
of a drive
head for driving the polished rod.


13. A clamp as defined in any of claims 1 to 12, further including means for
centering
said polished rod in said bore of said clamp body.


14. A clamp as defined in any of claims 1 to 13, further including means for
axially
locating said clamp members in said clamp body and for transferring axial and
rotational
loads from said clamp members to said clamp body.


15. A polished rod lock out clamp for use to temporarily suspend a polished
rod in an oil
well installation, comprising:
a clamp body having a bore therethrough for receiving the polished rod in
spaced
relation to said bore;
metal clamp members in said clamp body for engaging the polished rod in said
bore,
each said clamp member being radially movable with respect to the polished rod
and each



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having a recess formed therein for grippingly receiving and engaging said
polished rod for
metal to metal contact therewith; and
manipulating means secured to said clamp body and said clamp members for
moving
said clamp members between a polished rod gripping position in which said
clamp members
grippingly engage the polished rod to prevent rotation or axial movement
thereof and a
retracted position in which said clamp members are removed from the polished
rod to permit
rotational and axial movement of the polished rod in said bore of said clamp
body.


16. A clamp as defined in claim 15, wherein the diameter of said recess is
slightly less
than the diameter of the outer surface of said polished rod to enhance
gripping force.


17. A clamp as defined in claims 15 or 16, said clamp body further having
piston bores
extending radially of said bore of said clamp body, each said clamp member
comprising a
piston disposed in a piston bore, each piston having an inner end in which
said recess is
formed for receiving and grippingly engaging the polished rod.


18. A clamp as defined in claim 17, comprising a pair of said pistons radially
opposed to
one another.


19. A clamp as defined in claims 15 or 16, wherein said clamp members comprise
two
or more opposed clamp members each forming an elongated segment of a cylinder
and each
having said recess formed therein for engagement with the polished rod and an
arcuate outer
surface for engagement with said bore of said clamp body.


20. A clamp as defined in claims 15,16,17,18 or 19, said manipulating means
including
a bolt secured to each said clamp member, said bolts being threadedly engaged
with
respective radially extending threaded holes in said clamp body for radial
movement of said
bolts and said clamp members, said bolts extending outwardly of said clamp
body for
manipulation thereof.


21. A clamp as defined in any of claims 15 to 20, each said clamp member
having a
dovetail slot and a dovetail key formed on inner ends of said bolts for mating
engagement
with said dovetail slots for securing said bolts and associated clamp members.



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22. A clamp as defined in any of claims 15 to 21 including resilient members
disposed
between said clamp members to normally bias said clamp members towards said
retracted
position thereof.


23. A combined blow out preventer and polished rod lock out clamp for use in
an oil well
installation, comprising:
a housing having a bore for receiving a polished rod in spaced relation
therethrough
and opposed bores extending radially of said bore of said housing;
clamp members in said housing for grippingly engaging said polished rod in
said bore,
each said clamp member comprising a metallic piston disposed in one of said
radial bores,
each piston having an inner end and a concavely curved recess in said inner
end for
receiving and grippingly engaging said polished rod in metal to metal contact
along at least
a portion of the length of said recess to suspend said polished rod in said
oil well installation;
elastomeric seal means to provide a seal between a portion of the length of
said
recess in said piston and said polished rod, a seal between said pistons and
sealing of each
piston in its associated radial bore to prevent well fluid from coming up a
well bore and
escaping to the exterior of the well bore when said pistons grippingly engage
the polished
rod; and
manipulating means secured to said housing and said pistons for moving said
pistons
between a polished rod gripping position in which said pistons grippingly
engage said
polished rod to prevent rotation or axial movement thereof and a retracted
position in which
said pistons are removed from said polished rod to permit rotational and axial
movement of
said polished rod in said bore of said clamp housing.


24. A clamp as defined in claim 23, wherein said manipulating means include a
bolt
secured to each said piston, said bolts being threadedly engaged with radially
extending
threaded holes in said clamp body for radial movement of said bolts and said
pistons, said
bolts extending outwardly of said clamp body for manipulation thereof.


25. A clamp as defined in claims 23 or 24 including resilient members disposed
between
said clamp members to normally bias said clamp members towards said retracted
position
thereof.


26. A clamp as defined in claim 23, 24 or 25, wherein the diameter of said
curved recess
is slightly less than the diameter of the outer surface of the polished rod.



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27. The clamp as defined in claim 24,25 or 26, wherein each said bolt includes
a shaped
portion formed on an inner end thereof for mating engagement with a
correspondingly
shaped slot in a respective clamp member for moving said members into said
retracted
position thereof.


28. A polished rod lock out clamp operable to suspend a polished rod in an oil
well
installation, comprising:
a clamp body having an axial bore for receiving the polished rod in spaced
relation
to said bore;
clamp members in said clamp body having an elongated arcuate inner metallic
surface for grippingly engaging the polished rod in metal to metal contact,
each said clamp
member being radially moveable with respect to the polished rod; and
radially disposed bolts threaded into said clamp body for manipulation of said
clamp
members for moving said clamp members between a polished rod gripping position
in which
said clamp members grippingly engage said polished rod to prevent rotation or
axial
movement of the polished rod and a retracted position in which said clamp
members are
removed from the polished rod to permit rotational and axial movement of the
polished rod
relative to said axial bore of said clamp body.


29. A clamp as defined in claim 28, wherein said radially disposed bolts have
T-shaped
inner portions to hook into correspondingly shaped slots in said clamp members
to move said
clamp members to said retracted position thereof.


30. A clamp as defined in claims 28 or 29, wherein said clamp members comprise
a pair
of opposed clamp members each forming an elongated segment of a cylinder and
each
having on an inner surface thereof said arcuate inner surface for engagement
with the
polished rod, and a curved outer surface for contact with said bore of said
clamp body.


31. A clamp as defined in claim 28 or 29, wherein each said clamp member is in
the form
of a piston, said clamp body having a piston bore for each said piston, each
said piston bore
extending radially of said axial bore of said clamp body, each said piston
having an inner end
proximate said axial bore of said clamp body, said arcuate inner surface being
formed in said
inner end to be semi-circular in shape for receiving and grippingly engaging
said polished
rod.



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32. A clamp as defined in claim 31, comprising a pair of said pistons radially
opposed to
one another.


33. A clamp as defined in any of claims 27 to 31, wherein the diameter of said
arcuate
inner surface is slightly less than the diameter of the outer surface of the
polished rod for
enhanced gripping force.


34. A clamp as defined in claims 31, 32 or 33, said pistons having mutually
engageable
end faces at said inner ends thereof and seal means disposed between said end
faces, said
pistons being sealingly disposed in said piston bores and being sealingly
engageable with
said polished rod and with each other to prevent well fluids from escaping
past said clamp
when said pistons are disposed in said gripping positions thereof.


35. A polished rod lock out clamp, with blow out preventer seals, operable to
suspend a
polished rod in an oil well installation, comprising:
a clamp body having an axial bore for receiving the polished rod in spaced
relation
to said bore;
two radially opposed pistons acting as clamp members, said clamp body having a

piston bore for each said piston, each said piston bore extending radially of
said axial bore
of said clamp body, each said piston having an inner end proximate said axial
bore of said
clamp body, an arcuate inner surface being formed in said inner end to be semi-
circular in
cross-sectional shape for receiving and grippingly engaging said polished rod
in metal to
metal contact;
radially disposed bolts threaded into said clamp body for manipulation of said
pistons
for moving said pistons between a polished rod gripping position in which said
pistons
grippingly engage the polished rod to prevent rotation or axial movement of
the polished rod
and a retracted position in which said pistons are removed from the polished
rod to permit
rotational and axial movement of the polished rod in said axial bore of said
clamp body; and
said pistons each having an elastomeric seal to seal between the polished rod
and
a portion of the length of said arcuate inner surface in each said piston,
between said
opposed pistons and between each said piston and its associated radial bore to
prevent well
fluids from escaping from the well bore, said elastomeric seals being
compressible to allow
said pistons to make metal to metal contact with said polished rod when said
pistons are in
said gripping position thereof.



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36. A clamp as defined in claim 35, wherein the radius
of curvature of said arcuate inner surface is slightly less
than the radius of curvature of the outer surface of the

polished rod.


37. A clamp as defined in claims 35 or 36, wherein
said radially disposed bolts have T-shaped inner portions to
hook into correspondingly shaped slots in said clamp members
to retract said clamp members to said retracted positions
thereof.


38. A polished rod lock out clamp operable to suspend
a polished rod in an oil well installation, comprising:

a clamp body having a bore for receiving the
polished rod therethrough in spaced relation to said bore;
clamp members in said clamp body for gripping the
polished rod in said bore; and

manipulating means secured to said clamp body and
said clamp members for moving said clamp members between a
polished rod gripping position in which said clamp members
grippingly engage said polished rod in non-elastomeric
frictional contact therebetween to prevent rotation or axial
movement of the polished rod, and a retracted position in
which said clamp members are removed from the polished rod
to permit rotational and axial movement of the polished rod
in said bore of said clamp body.


39. A polished rod lock out clamp operable to suspend
a polished rod in an oil well installation, comprising:

a clamp body having a bore for receiving the
polished rod therethrough in spaced relation to said bore;



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clamp members in said clamp body for gripping the
polished rod in said bore; and

manipulating means secured to said clamp body and
said clamp members for moving said clamp members between a
polished rod gripping position in which said clamp members
grippingly engage said polished rod in hard surface to hard
surface contact therebetween to prevent rotation or axial
movement of the polished rod, and a retracted position in
which said clamp members are removed from the polished rod
to permit rotational and axial movement of the polished rod
in said bore of said clamp body.


40. A clamp as defined in claims 38 or 39, each said
clamp member being radially movable with respect to said
polished rod and having an arcuate inner surface for
engaging said polished rod thereinto.


41. A clamp as defined in claim 40, wherein the
diameter of said inner surface is slightly less than the
diameter of the polished rod to enhance gripping force.

42. A clamp as defined in claims 38, 39, 40 or 41,
wherein each said clamp member is in the form of a piston,
said clamp body having a piston bore for each said piston,
each said piston bore extending radially of said bore of
said clamp body.


43. A clamp as defined in claim 42, comprising a pair
of said pistons radially opposed to one another.


44. A clamp as defined in claim 43, said pistons
having mutually engageable end faces at said inner ends
thereof and seal means disposed between said end faces, said
pistons being sealingly disposed in said piston bores and



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being sealingly engageable with said polished rod and with
each other to prevent well fluids from escaping past said
clamp when said pistons are disposed in said gripping

positions thereof.


45. A clamp as defined in claims 40 or 41, said clamp
members comprising a pair of opposed clamp members each
forming an elongated segment of a cylinder.


46. A polished rod lock out clamp for use to
temporarily suspend a polished rod in an oil well
installation, comprising:

a clamp body having a bore therethrough for
receiving the polished rod in spaced relation to said bore;
clamp members in said clamp body for engaging the
polished rod in said bore, each said clamp member being
radially movable with respect to the polished rod and each
having a recess formed therein for grippingly receiving and
engaging said polished rod for non-elastomeric frictional
contact therewith; and

manipulating means secured to said clamp body and
said clamp members for moving said clamp members between a
polished rod gripping position in which said clamp members
grippingly engage the polished rod to prevent rotation or
axial movement thereof and a retracted position in which
said clamp members are removed from the polished rod to
permit rotational and axial movement of the polished rod in
said bore of said clamp body.


47. A polished rod lock out clamp for use to
temporarily suspend a polished rod in an oil well
installation, comprising:



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a clamp body having a bore therethrough for
receiving the polished rod in spaced relation to said bore;

clamp members in said clamp body for engaging the
polished rod in said bore, each said clamp member being
radially movable with respect to the polished rod and each
having a recess formed therein for grippingly receiving and
engaging said polished rod for hard surface to hard surface
contact therewith; and

manipulating means secured to said clamp body and
said clamp members for moving said clamp members between a
polished rod gripping position in which said clamp members
grippingly engage the polished rod to prevent rotation or
axial movement thereof and a retracted position in which
said clamp members are removed from the polished rod to
permit rotational and axial movement of the polished rod in
said bore of said clamp body.

48. A clamp as defined in claims 46 or 47, wherein the
diameter of said recess is slightly less than the diameter
of the outer surface of said polished rod to enhance
gripping force.

49. A clamp as defined in claims 46, 47, or 48, said
clamp body further having piston bores extending radially of
said bore of said clamp body, each said clamp member
comprising a piston disposed in a piston bore, each piston
having an inner end in which said recess is formed for
receiving and grippingly engaging the polished rod.

50. A clamp as defined in claim 49, comprising a pair
of said pistons radially opposed to one another.

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51. A clamp as defined in claims 46, 47 or 48, wherein
said clamp members comprise two or more opposed clamp
members each forming an elongated segment of a cylinder and
each having said recess formed therein for engagement with
the polished rod and an arcuate outer surface for engagement
with said bore of said clamp body.

52. A combined blow out preventer and polished rod
lock out clamp for use in an oil well installation,
comprising:

a housing having a bore for receiving a polished
rod in spaced relation therethrough and opposed bores
extending radially of said bore of said housing;

clamp members in said housing for grippingly
engaging said polished rod in said bore, each said clamp
member comprising a piston disposed in one of said radial
bores, each piston having an inner end and a concavely
curved recess in said inner end for receiving and grippingly
engaging said polished rod in non-elastomeric frictional
contact along at least a portion of the length of said
recess to suspend said polished rod in said oil well
installation;

elastomeric seal means to provide a seal between a
portion of the length of said recess in said piston and said
polished rod, a seal between said pistons and sealing of
each piston in its associated radial bore to prevent well
fluid from coming up a well bore and escaping to the
exterior of the well bore when said pistons grippingly
engage the polished rod; and

manipulating means secured to said housing and
said pistons for moving said pistons between a polished rod
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gripping position in which said pistons grippingly engage
said polished rod to prevent rotation or axial movement
thereof and a retracted position in which said pistons are
removed from said polished rod to permit rotational and
axial movement of said polished rod in said bore of said
clamp housing.

53. A combined blow out preventer and polished rod
lock out clamp for use in an oil well installation,
comprising:

a housing having a bore for receiving a polished
rod in spaced relation therethrough and opposed bores
extending radially of said bore of said housing;

clamp members in said housing for grippingly
engaging said polished rod in said bore, each said clamp
member comprising a piston disposed in one of said radial
bores, each piston having an inner end and a concavely
curved recess in said inner end for receiving and grippingly
engaging said polished rod in hard surface to hard surface
contact along at least a portion of the length of said
recess to suspend said polished rod in said oil well
installation;

elastomeric seal means to provide a seal between a
portion of the length of said recess in said piston and said
polished rod, a seal between said pistons and sealing of
each piston in its associated radial bore to prevent well
fluid from coming up a well bore and escaping to the
exterior of the well bore when said pistons grippingly
engage the polished rod; and

manipulating means secured to said housing and
said pistons for moving said pistons between a polished rod
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gripping position in which said pistons grippingly engage
said polished rod to prevent rotation or axial movement
thereof and a retracted position in which said pistons are
removed from said polished rod to permit rotational and
axial movement of said polished rod in said bore of said
clamp housing.

54. A clamp as defined in claims 52 or 53, wherein the
diameter of said curved recess is slightly less than the
diameter of the outer surface of the polished rod.

55. A polished rod lock out clamp, with blow out
preventer seals, operable to suspend a polished rod in an
oil well installation, comprising:

a clamp body having an axial bore for receiving
the polished rod in spaced relation to said bore;

two radially opposed pistons acting as clamp
members, said clamp body having a piston bore for each said
piston, each said piston bore extending radially of said
axial bore of said clamp body, each said piston having an
inner end proximate said axial bore of said clamp body, an
arcuate inner surface being formed in said inner end for
receiving and grippingly engaging said polished rod in metal
to metal contact;

manipulating means secured to said clamp body and
said clamp members for moving said pistons between a
polished rod gripping position in which said pistons
grippingly engage the polished rod to prevent rotation or
axial movement of the polished rod and a retracted position
in which said pistons are removed from the polished rod to
permit rotational and axial movement of the polished rod in
said axial bore of said clamp body;
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and said pistons each having an elastomeric seal
to seal between the polished rod and a portion of the length
of said arcuate inner surface in each said piston, between
said opposed pistons and between each said piston and its
associated radial bore to prevent well fluids from escaping
from the well bore, said elastomeric seals being
compressible to allow said pistons to make metal to metal
contact with said polished rod when said pistons are in said
gripping position thereof.

56. A polished rod lock out clamp, with blow out
preventer seals, operable to suspend a polished rod in an
oil well installation, comprising:

a clamp body having an axial bore for receiving
the polished rod in spaced relation to said bore;

two radially opposed pistons acting as clamp
members, said clamp body having a piston bore for each said
piston, each said piston bore extending radially of said
axial bore of said clamp body, each said piston having an
inner end proximate said axial bore of said clamp body, an
arcuate inner surface being formed in said inner end for
receiving and grippingly engaging said polished rod in hard
surface to hard surface contact;

manipulating means secured to said clamp body and
said clamp members for moving said pistons between a
polished rod gripping position in which said pistons
grippingly engage the polished rod to prevent rotation or
axial movement of the polished rod and a retracted position
in which said pistons are removed from the polished rod to
permit rotational and axial movement of the polished rod in
said axial bore of said clamp body;


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and said pistons each having an elastomeric seal
to seal between the polished rod and a portion of the length
of said arcuate inner surface in each said piston, between
said opposed pistons and between each said piston and its
associated radial bore to prevent well fluids from escaping
from the well bore, said elastomeric seals being
compressible to allow said pistons to make hard surface to
hard surface contact with said polished rod when said
pistons are in said gripping position thereof.

57. A polished rod lock out clamp, with blow out
preventer seals, operable to suspend a polished rod in an
oil well installation, comprising:

a clamp body having an axial bore for receiving
the polished rod in spaced relation to said bore;

two radially opposed pistons acting as clamp
members, said clamp body having a piston bore for each said
piston, each said piston bore extending radially of said
axial bore of said clamp body, each said piston having an
inner end proximate said axial bore of said clamp body, an
arcuate inner surface being formed in said inner end for
receiving and grippingly engaging said polished rod in non-
elastomeric frictional contact;

manipulating means secured to said clamp body and
said clamp members for moving said pistons between a
polished rod gripping position in which said pistons
grippingly engage the polished rod to prevent rotation or
axial movement of the polished rod and a retracted position
in which said pistons are removed from the polished rod to
permit rotational and axial movement of the polished rod in
said axial bore of said clamp body;

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and said pistons each having an elastomeric seal
to seal between the polished rod and a portion of the length
of said arcuate inner surface in each said piston, between
said opposed pistons and between each said piston and its
associated radial bore to prevent well fluids from escaping
from the well bore, said elastomeric seals being
compressible to allow said pistons to make non-elastomeric
frictional contact with said polished rod when said pistons
are in said gripping position thereof.

58. A clamp as defined in claims 55, 56 or 57, wherein
the radius of curvature of said arcuate inner surface is
slightly less than the radius of curvature of the outer
surface of the polished rod.

59. A clamp as defined in any of claims 35 to 37, 55
or 58, wherein said elastomeric seal is mounted in a groove
in said arcuate inner surface in each piston, and is
compressible into said groove to allow said pistons to make
metal to metal contact with said polished rod when said
pistons are in said gripping position thereof.

60. A clamp as defined in claims 56 or 58, wherein
said elastomeric seal is mounted in a groove in said arcuate
inner surface in each piston, and is compressible into said
groove to allow said pistons to make hard surface to hard
surface contact with said polished rod when said pistons are
in sa-id gripping position thereof.

61. A clamp as defined in claims 57 or 58, wherein
said elastomeric seal is mounted in a groove in said arcuate
inner surface in each piston, and is compressible into said
groove to allow said pistons to make non-elastomeric

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frictional contact with said polished rod when said pistons
are in said gripping position thereof.

62. A clamp as defined in any of claims 1 to 61,
wherein a non-metallic coating is applied to the gripping
surface of the clamp members.

63. A clamp as defined in claim 62, wherein said non-
metallic coating comprises an oxide, carbide or ceramic
selected to decrease the wear of said clamp members or to
increase the gripping properties of the contact between said
clamp members and the polished rod.


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Description

CA 02349988 2005-05-12

POLISH ROD LOCKING CLAMP
FIELD OF THE INVENTION
The present invention relates generally to progressing cavity pump oil well
installations and, more specifically, to a polished rod lock out clamp for use
in progressing
cavity pump oil well installations.

BACKGROUND OF THE INVENTION
Progressing cavity pump drives presently on the market have weaknesses with
respect to the stuffing box maintenance. Oil producing companies need a pump
drive which
requires little or no maintenance, is very safe for operating personnel and
minimizes the
chances of product leakage and resultant environmental damage. When
maintenance is
required on the pump drive, it must be safe and very fast and easy to do.
Due the abrasive sand particles present in crude oil and poor alignment
between the
wellhead and stuffing box, leakage of crude oil from the stuffing box is
common in some
applications. This costs oil companies money in service time, down time and
environmental
clean up. It is especially a problem in heavy crude oil wells in which the oil
is often produced
from semi-consolidated sand formations since loose sand is readily transported
to the
stuffing box by the viscosity of the crude oil. Costs associated with stuffing
box failures are
one of the highest maintenance costs on many wells.
Servicing of stuffing boxes is time consuming and difficult. Existing stuffing
boxes are
mounted below the drive head. Stuffing boxes are typically separate from the
drive and are
mounted in a wellhead frame such that they can be serviced from below the
drive head
without removing it. This necessitates mounting the drive head higher,
constrains the design
and still means a difficult service job. Drive heads with integral stuffing
boxes mounted on
the bottom of the drive head have more recently entered the market. In order
to service the
stuffing box, the drive must be removed which necessitates using a rig with
two winch lines,
one to support the drive and the other to hold the polished rod. This is more
expensive and
makes servicing the stuffing box even more difficult. As a result, these
stuffing boxes are
typically exchanged in the field and the original stuffing box is sent back to
a service shop for
repair-still unsatisfactory.
Prior art blow out preventers, while similar in structure, are not intended to
grip the
polished rod in metal to metal contact to suspend a polished rod and prevent
axial or angular
displacement of the polished rod. The function of the narrow elastomeric seal
as sometimes
used on existing blow out preventers is only to seal between the pistons,
between the pistons
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CA 02349988 2005-05-12

and the polished rod and between the pistons and the piston bores. The reason
for using
a narrow elastomeric seal is that this construction has enhanced sealing at
high pressure
compared to blow out preventer pistons that are predominantly elastomeric with
steel inserts
for engaging with the actuating means. Existing blow out preventers have the
grooves in the
pistons substantially filled with the elastomeric seal and at the piston face
the elastomeric
seal projects beyond the piston face. When the pistons are closed together the
elastomeric
seals cannot be pushed into the grooves since the grooves are already
substantially filled by
the elastomeric seal, Seal volume in prior art exceeds the volume of the
grooves in the
piston. Thus, metal to metal contact between the pistons and the polish rod
cannot be
achieved because the seals always project beyond the piston face. Contact
between the
polished rod and the elastomeric seal is not adequate to suspend the polished
rod weight
because of the shear stress limitations of the elastomer and the lower
coefficient of friction
between the elastomer and the polish rod in a wetted condition. Additionally,
the enhanced
gripping force that can be achieved by making the radius on the piston face
smaller than the
radius of the polished rod is substantial but cannot be achieved without metal
to metal
contact.

SUMMARY OF THE INVENTION
The present invention seeks to simplify the issue of stuffing box maintenance
by
eliminating the need to support a polish rod with a rig and winch line during
such
maintenance. In order to eliminate the need for a rig, the present invention
provides a
special clamp integrated with or below the drive head to support the polished
rod and prevent
rotation while the stuffing box is serviced. Blow out preventers can be
integrated into the
clamping means and are therefore closed while the stuffing box is serviced,
thus preventing
any well fluids from escaping while the stuffing box is open.
According to the present invention then, there is provided a polished rod lock
out
ciamp operable to suspend a polished rod in an oil well installation,
comprising a clamp body
having a bore for receiving the polished rod therethrough in spaced relation
to said bore;
clamp members in said clamp body for gripping the polished rod in said bore;
and
manipulating means secured to said clamp body and said clamp members for
moving said
clamp members between a polished rod gripping position in which said clamp
members
grippingly engage said polished rod in metal to metal contact therebetween to
prevent
rotation or axial movement of the polished rod, and a retracted position in
which said clamp
members are removed from the polished rod to permit rotational and axial
movement of the
polished rod in said bore of said clamp body.

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CA 02349988 2005-05-12

According to another aspect of the present invention, there is provided a
polished rod
lock out clamp for use to temporarily suspend a polished rod in an oil well
installation,
comprising a clamp body having a bore therethrough for receiving the polished
rod in spaced
relation to said bore; metal clamp members in said clamp body for engaging the
polished rod
in said bore, each said clamp member being radially movable with respect to
the polished rod
and each having a recess formed therein for grippingly receiving and engaging
said polished
rod for metal to metal contact therewith; and manipulating means secured to
said clamp body
and said clamp members for moving said clamp members between a polished rod
gripping
position in which said clamp members grippingly engage the polished rod to
prevent rotation
or axial movement thereof and a retracted position in which said clamp members
are
removed from the polished rod to permit rotational and axial movement of the
polished rod
in said bore of said clamp body.
In a still further embodiment of the present invention, there is provided a
combined
blow out preventer and polished rod lock out clamp for use in an oil well
installation,
comprising a housing having a bore for receiving a polished rod in spaced
relation
therethrough and opposed bores extending radially of said bore of said
housing; clamp
members in said housing for grippingly engaging said polished rod in said
bore, each said
clamp member comprising a metallic piston disposed in one of said radial
bores, each piston
having an inner end and a concavely curved recess in said inner end for
receiving and
grippingly engaging said polished rod in metal to metal contact along at least
a portion of the
length of said recess to suspend said polished rod in said oil well
installation; eiastomeric
seal means to provide a seal between a portion of the length of said recess in
said piston and
said polished rod, a seal between said pistons and sealing of each piston in
its associated
radial bore to prevent well fluid from coming up a well bore and escaping to
the exterior of
the well bore when said pistons grippingly engage the polished rod; and
manipulating means
secured to said housing and said pistons for moving said pistons between a
polished rod
gripping position in which said pistons grippingly engage said polished rod to
prevent rotation
or axial movement thereof and a retracted position in which said pistons are
removed from
said polished rod to permit rotational and axial movement of said polished rod
in said bore
of said clamp housing.
In yet a further embodiment of the present invention, there is provided a
polished rod
lock out clamp operable to suspend a polished rod in an oil well installation,
comprising a
clamp body having an axial bore for receiving the polished rod in spaced
relation to said
bore; clamp members in said clamp body having an elongated arcuate inner
metallic surface
for grippingly engaging the polished rod in metal to metal contact, each said
clamp member
being radially moveable with respect to the polished rod; and radially
disposed bolts threaded
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CA 02349988 2005-05-12

into said clamp body for manipulation of said clamp members for moving said
clamp
members between a polished rod gripping position in which said clamp members
grippingly
engage said polished rod to prevent rotation or axial movement of the polished
rod and a
retracted position in which said clamp members are removed from the polished
rod to permit
rotational and axial movement of the polished rod relative to said axial bore
of said clamp
body.
In still yet another embodiment of the present invention, there is provided a
polished
rod lock out clamp, with blow out preventer seals, operable to suspend a
polished rod in an
oil well installation, comprising a clamp body having an axial bore for
receiving the polished
rod in spaced relation to said bore; two radially opposed pistons acting as
clamp members,
said clamp body having a piston bore for each said piston, each said piston
bore extending
radially of said axial bore of said clamp body, each said piston having an
inner end proximate
said axial bore of said clamp body, an arcuate inner surface being formed in
said inner end
to be semi-circular in cross-sectional shape for receiving and grippingly
engaging said
polished rod in metal to metal contact; radially disposed bolts threaded into
said damp body
for manipulation of said pistons for moving said pistons between a polished
rod gripping
position in which said pistons grippingly engage the polished rod to prevent
rotation or axial
movement of the polished rod and a retracted position in which said pistons
are removed
from the polished rod to permit rotational and axial movement of the polished
rod in said axial
bore of said clamp body; and said pistons each having an elastomeric seal to
seal between
the polished rod and a portion of the length of said arcuate inner surface in
each said piston,
between said opposed pistons and between each said piston and its associated
radial bore
to prevent well fluids from escaping From the well bore, said elastomeric
seals being
compressible to aliow said pistons to make metal to metal contact with said
polished rod
when said pistons are in said gripping position thereof.

BRIEF DESCRIPTION OF THE DRAWINGS
This and other features of preferred embodiments of the present invention will
become more apparent from the following description in which reference is made
to the
appended drawings in which:
Figure 1 is a view of a progressing cavity pump oil well installation in an
earth
formation with a typical drive head, wellhead frame and stuffing box;
Figure 2 is a view similar to the upper end of Figure 1 but i{iustrating a
conventional
drive head with an integrated stuffing box extending from the bottom end of
the drive head;
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CA 02349988 2005-05-12

Figure 3 is a side elevational, cross-sectional view of one embodiment of a
polished
rod lock-out damp according to the present invention;
Figure 4 is a top plan view of the clamp of Figure 3;
Figure 5 is a side elevational, cross-sectional view of another embodiment of
a
polished rod lock-out clamp according to the present invention;
Figure 6 is a top plan view of the claim of Figure 4;
Figure 7is a side elevational, cross-sectional view of another embodiment of a
polished rod lock-out clamp according to the present invention;
Figure 8 is a top plan view of the clamp of Figure 7;
Figure 9 is a side elevational, cross-sectional view of one embodiment of a
blow out
preventer having an integrated polished rod lock-out clamp according to the
present
invention; and
Figure 10 is a top plan view of the clamp of Figure 9.
Figure 11 is a view of the drive head of Figure 2 with a cross-sectional view
of a
polished rod lock out clamp connected.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Figure 1 illustrates a known progressing cavity pump installation 10. The
installation
includes a typical progressing cavity pump drive head 12 , a wellhead frame 14
, a stuffing
box 16 , an electric motor 18, and a belt and sheave drive system 20, alt
mounted on a flow
tee 22. The flow tee is shown with a blow out preventer 24 which is, in tum,
mounted on a
wellhead 25. The drive head supports and drives a drive shaft 26, generally
known as a
"polished rod". The polished rod is supported and rotated by means of a polish
rod clamp
28, which engages an output shaft 30 of the drive head by means of milled
slots (not shown)
in both parts. Wellhead frame 14 is open sided in order to expose polished rod
26 to allow
a service crew to install a safety clamp on the polished rod and then perform
maintenance
work on stuffing box 16 . Polished rod 26 rotationally drives a drive string
32, sometimes
referred to as "sucker rods", which, in tum, drives a progressing cavity pump
34 located at
the bottom of the installation to produce well fluids to the surface through
the wellhead.
Figure 2 illustrates a typical progressing cavity pump drive head 36 with an
integral
stuffing box 38 mounted on the bottom of the drive head and corresponding to
that portion
of the installation in Figure 1 which is above the dotted and dashed line 40.
The main
advantage of this type of drive head is that, since the main drive head shaft
is already
supported with bearings, stuffing box seals can be placed around the main
shaft, thus
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CA 02349988 2005-05-12

improving alignment and eliminating contact between the stuffing box rotary
seals and the
polished rod. This style of drive head reduces the height of the installation
because there
is no wellhead frame and also reduces cost because there is no wellhead frame
and there
are fewer parts since the stuffing box is integrated with the drive head. The
main
disadvantage is that the drive head must be removed to do maintenance work on
the stuffing
box. This necessitates using a service rig with two lifting lines, one to
support the polished
rod and the other to support the drive head.
In order to overcome the above disadvantages, the present invention provides a
polished rod lock-out clamp for use in clamping the polished rod during drive
head servicing
operations. The clamp can be integrated with the drive head or provided as a
separate
assembly below the drive.
One aspect of the present invention is the provision of a polished rod lock
out clamp
160 for use in securing the polished rod when it is desired to service the
drive head. The
clamp may be integrated into the drive head or may be provided as a separate
assembly,
which is secured to and between the drive head and a flow tee, as illustrated
in Figure 11.
Figures 3-6 illustrate two embodiments of a lock-out clamp. As shown, in each
embodiment,
the clamp includes a tubular clamp body 162 having a bore 164 for receiving
polished rod
26 in annularly spaced relation therethrough. A bushing 166 is mounted on an
annular
shoulder 168 formed at the bottom end of bore 164 for centering the polished
rod in the
housing. Flanges 167 or threaded connections depending on the application are
formed at
the upper and lower ends of the housing for bolting or otherwise securing the
housing to the
underside of the drive head and to the upper end of the flow tee. The clamp
includes two or
more equally angularly spaced clamp members or shoes 170 about the axis of the
housing/polished rod. The clamp shoes are generally in the form of a segment
of a cylinder
with an arcuate inner surface 172 dimensioned to correspond to the curvature
of the surface
of the polished rod. Arcuate inner surfaces 172 should be undersize relative
to the polished
rod's diameter to enhance gripping force. In the embodiment of Figures 3 and
4, spring
means 174 are provided to normally bias the clamp members into an un-clamped
position.
In the embodiment of Ftgures 5 and 6, the ends of bolts 176 are generally T-
shaped to hook
into correspondingly shaped slots 169 in shoes 170 to positively retract the
shoes without the
need for springs 174.
Clamp shoes 170 are actuated by radial bolts 176, for example, to clamp the
polished
rod such that it cannot turn or be displaced axially. The lock out clamp may
be located
between the flow tee and the bottom of the drive head. Alternately, it can be
built into the
drive head.

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CA 02349988 2005-05-12

In some appNcaUons It Is preferable not to restrict the diameter through the
bore 1 di
of the lodc out damp so that the sudcer rods can be pulled tlrough the damp
160. In thils
embodiment of the polish rod damp as shown in Figure 7 and 8, where Iike
numerals
identity like elements, two opposing radial pistona 182 are actuated by bolts
184 to force the
piskns togedhar and anwnd pdish rod Ze. The poAsh rod is gipped by waate
reoesses
1 Sd, which are preferably made undersize reiative to the polisftted rod to
enhance grippinp
force. Pistons 182 further indude 0-rings 223 to provkie a bettsr seai In
bore.164:
In a furlher embodiment of the poNshed rod todc out damp, the damping means
are
integrated with a bbw out preventer 180, shown in Figuns 9 and 10. Bkyw out
pr+avenesrs
are required on most oil weps. They traditionaNy have two opposing radial
pistons 182
actuated by bolts 184 to force ft pistons together and around the poiish rod
to effed a seal.
The pistons are generally made of eiastomsr or provided with an elastomsdc
Bner such that
when the pistons are forced together by the bolts, a seal Is formed betvireen
the pistons,
between the pistons and the polish rod and between the pistons and the piston
bores.
Actuation thus serves as a means to prevent weN flukb from escaping from the
weN.
In accordance with the present invention, an improved blow out preventsr
satves as
a lock out damp for'weN servidng. In order to serve this purpose, the pistons
must be
substantisk of metal which can be forced against the poflshed rod to prevent
axial or
rotationsi motion thereof. The Inner end of the pistons Is formed with an
arcuate recess 1SO
with curvatufe corresponding substantlapy to that of the polished rod.
Enhanoed gripping
torcre can be adNeved if the arouate recoss diameter Is undenrize relatlve to
the polistbd rod.
The sealing function oi the blow out preventsr must still be acoomplished.
This can be done
by providing a narrow elastomeric seal 188 which runs across the vertical flat
face of the
piston, akmg the arc.vate recess; a"the mid heigM of the piston and then
dnxunterentiaaNy,
around the piston. The seals can compress Into the grooves which pennits the
platons to
engage the polished rod In metal to metal contaat. Seal 188 seais between the
pistons,
between the pistons and the poqsh rod and between the pistons and the piston
bores. Thus,
well fluid is prevented from,coming up the well bore and escaphg while the wep
Is being
serviced, as might be the case while the stufflng box Is being repaired. By
induding tha
sealing func8on d the BOP with clamping means, one set of pistons can
aooompHah both
functions, enhancing safety and convenience without increasing cost or size.
It will be understood by one skilled in the art that, in stating that the
pistons must be
substantially of metal, and that the pistons engage the polished md in metal
to metal
contact, it Is not intended to exdude the use of conventional non-metallic
coatings that may be
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CA 02349988 2005-05-12

added to metallic surfaces for enhanced wear and/or gripping properties, such
as
certain oxides, carbides and ceramics.
The above-described embodiments of the present invention are meant to be
illustrative of preferred embodiments and are not intended to 1imk the scope
of the
present inventlon. Varbus modHications, which would be'neadily apparent to one
skiibd
in the art, are intended to be within the scope of the present invention. The
only
limitations to the scope of the present invention are set. forth in the
folkrwing clairhs
appended hereto.

-8-

Representative Drawing