Wrench assembly for a top drive sub

A wrench assembly for making and breaking connections between tubular members, such as a drill string and a top drive sub. The wrench assembly consists of a lower wrench and an upper wrench. The lower wrench has a curved gate arm and a curved latch arm, pivotable between an open position and a closed position. The gate arm has a plurality of teeth on its outer surface, and the latch arm has a plurality of teeth on its inner surface, for locking engagement with the teeth on the gate arm. The lower wrench also has a clamping cylinder and a die block for forcing the tubular member against the gate arm. The upper wrench, mounted above the lower wrench, has a semicircular plate. A plurality of splines are mounted on the interior surface of the semicircular plate for engagement with splines on the top drive sub. A fluid cylinder is provided for applying torque to the wrenches to rotate one of the wrenches with respect to the other wrenches.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates in general to wrench assemblies and in particular to 
a wrench assembly for use with a top drive well drilling apparatus. 
2. Description of the Prior Art 
In the drilling of oil and gas wells, hydraulically powered wrenches are 
used to make and break connections between tubular members. The wrench 
assemblies generally used in these applications have a pair of wrenches, 
one mounted directly above the other. Each wrench grips a joint on either 
side of the connection, and torque is applied to rotate the wrenches with 
respect to one another, to make up or break the connection. One such 
wrench assembly is shown in U.S. Pat. No. 4,348,920 (BOYADJIEFF), issued 
Sept. 14, 1982. One disadvantage inherent in the prior art has been that 
the wrenches must be adjusted to accommodate tubular members of different 
diameters. 
A top drive drilling system rotates a drill string from the top, rather 
than using a rotary table, a kelly, and a kelly bushing. An electric 
drilling motor is suspended from the drilling rig's conventional swivel 
and is attached to the top of the drill string. The drilling motor may 
also be attached to a carriage, which is guided by a pair of vertical 
tracks. The drilling motor is connected to the drill string by a 
cylindrical stem, which extends downward from the motor. A top drive sub 
is the bottom unit of the cylindrical stem, and is the unit to which the 
drill string is threaded. A wrench assembly is also suspended from the 
drilling motor, in order to make or break connections between the top 
drive sub and the drill string. In some prior art top drive drilling 
systems, the wrench assembly rotates with the drill string and is not 
removable therefrom. However, there are some top drive well drilling 
apparatus in which the wrench assembly may be retracted away from the 
drill string. 
SUMMARY OF THE INVENTION 
The present invention is a wrench assembly which may be used, without 
adjustment, on tubular members having a wide range of diameters. The 
wrench assembly has a lower wrench, which has a curved gate arm and a 
curved latch arm, which are pivotally connected to the frame of the 
wrench. The gate arm has a plurality of teeth on its outer surface, and 
the latch arm has a plurality of teeth on its inner surface. When the gate 
arm and the latch arm have been closed against the tubular member, the 
teeth on the gate arm will engage certain teeth on the latch arm, 
depending upon the diameter of the tubular member being gripped. 
The upper wrench of the wrench assembly has a semicircular plate having a 
plurality of vertical splines. The splines, which are beveled on the upper 
end, are adapted to engage splines on the top drive sub in a top drive 
drilling system. When constructed according to the invention, the wrench 
assembly is capable of connecting and disconnecting connections between a 
top drive sub and a tool joint on a drill string regardless of the 
diameter of the tool joint. 
The above, as well as additional objects, features, and advantages of the 
invention, will become apparent in the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a top drive well drilling apparatus. A conventional 
traveling block 11 and a conventional hook 13 are suspended by cables 15 
above the floor 17 of an oil well drilling rig. A top drive unit 19, which 
is a drilling motor of a conventional type, is suspended from the hook 13. 
A carriage 21 guides the top drive unit 19 up and down along a pair of 
vertical guide tracks 23. A tubular member, or stem 25, extends downward 
from the top drive unit 19. The upper end of a drill string 27 is threaded 
to a top drive sub 29, which is the lowest unit of the stem 25. The drill 
string 27 consists of a series of tubular members, called pipe sections, 
and has a rotary rock bit attached at the lower end for drilling a well 
bore. 
A wrench assembly 31 is used to make and break connections in the stem 25 
and the connection between the top drive sub 29 and the drill string 27. 
The wrench assembly 31 is mounted on the carriage 21, and is movable 
horizontally between a working position along the stem 25, or the drill 
string 27, and a retracted position away from the axis of the drill string 
27. The wrench assembly 31 is also movable vertically along the stem 25 
and the drill string 27. When the wrench assembly 31 is used to make or 
break the connection between the drill string 27 and the top drive sub 29, 
the lower wrench 33 grips the tool joint 35 on the upper end of the drill 
string 27, and the upper wrench 37 engages the top drive sub 29. The top 
drive sub 29 has a plurality of splines 39 to facilitate the engagement 
between the wrench 37 and the sub 29. 
FIG. 2 shows the lower wrench 33 in the closed position. The lower wrench 
33 has a curved gate arm 41 and a curved latch arm 43, pivotally connected 
to a frame 45 at pivot points 47 and 49, respectively. The gate arm 41 and 
the latch arm 43 are pivotable between the closed position, as shown in 
FIG. 2, and an open position wherein the wrench can be applied to or 
removed from the tool joint 35. A fluid cylinder 51, 53 is connected to 
each arm 41, 43 to provide means for pivoting the arms between the open 
and closed positions. The gate arm 41 has a plurality of latching teeth 55 
on its outer surface, and the latch arm 43 has a plurality of latching 
teeth 57 on its inner surface for locking engagement with the teeth 55 on 
the gate arm 41. A die block 59, have tong dies 58, is mounted on the 
frame 45 opposite the gate arm 41 and latch arm 43. A clamping cylinder 61 
moves the die block 59 reciprocally between a retracted position away from 
the drill string 27 and an extended position against the drill string 27. 
The clamping cylinder 61 and die block 59 are a means for forcing the tool 
joint 35 against the gate arm 41. 
FIG. 3 illustrates how the wrench is capable of engaging tubular members of 
different diameters, without having to be adjusted. The solid lines show 
tong dies 60 on the gate arm 41 engaging a tubular member 62 of a larger 
diameter. The teeth 55 on the gate arm 41 engage the teeth 57 on the latch 
arm 43, and the specific teeth 57 which are engaged are near the outer end 
63 of the latch arm 43. When the gate arm 41 engages a tubular member 64 
of a smaller diameter, as shown in shadow in FIG. 3, the teeth 55 on the 
gate arm 41 engage a different set of teeth 57 on the latch arm 43. In 
this case, the engaged teeth 57 on the latch arm 43 are closer to the 
pivot point 49. For tubular members of various diameters, the gate arm 
teeth 55 will engage different latch arm teeth 57. Thus, the gate arm 41 
is capable of engaging tubular members having a wide range of diameters, 
without having to be adjusted. 
FIG. 4 shows the entire wrench assembly 31, which consists of the lower 
wrench 33 and an upper wrench 37. The upper wrench 37 does not completely 
encircle the top drive sub 29 but rather has a semicircular plate 65. A 
plurality of vertical splines 67 are mounted on the interior surface of 
the semicircular plate 65, for engaging the splines 39 on the top drive 
sub 29. The splines 67 on the upper wrench 37 are spaced apart so as to 
fit between the splines 39 on the top drive sub 29. The upper end of each 
spline 67 is beveled to facilitate engagement with the splines 39 on the 
top drive sub 29. A fluid cylinder 71 is attached to the lower wrench 33, 
and the piston rod 73 is connected to the upper wrench 37. When the piston 
rod 73 is extended, the upper wrench is rotated counterclockwise, relative 
to the lower wrench 33. The fluid cylinder 71 and piston rod 73 are thus 
means for applying torque to the wrenches 33, 37 to rotate one of the 
wrenches with respect to the other wrench. 
In operation, the wrench assembly 31 is first retracted away from the stem, 
and then lowered to a position below the connection between the tool joint 
35 and the top drive sub 29. The wrench assembly 31 is then extended back 
to the center line of the drill string 27. The wrench assembly 31 is 
raised to engage the splines 67 on the upper wrench 37 and the splines 39 
on the top drive sub 29. Interrotational capability is provided to align 
the splines 39, 67, aided by the bevels 69 at the top of the wrench 
splines 67. The splines 37 on the top drive sub 29 are beveled at the 
lower end. 
When the upper wrench 37 is aligned with the top drive sub 29, the lower 
wrench 33 will be aligned with the tool joint 35 at the top of the drill 
string 27. The fluid cylinder 51 is actuated to pivot the gate arm 41 to 
its closed position, in which the inner surface of the gate arm 41 
contacts the tool joint 35. Fluid cylinder 53 is then actuated to pivot 
the latch arm 43 to close onto the gate arm 41. The latching teeth 57 on 
the latch arm 43 may or may not mesh with the teeth 55 on the gate arm 41 
at this point. The clamping cylinder 61 is then actuated to extend the die 
block 59. The die block 59 pushes the tool joint 35 against the gate arm 
41. The clamping cylinder 61 exerts substantial pressure and overcomes the 
gate arm cylinder 51, causing the gate arm 41 to be pushed back. The gate 
arm 41 will continue to be pushed back until the teeth 55, 57 on the arms 
41, 43 become interlocked. The pressure in the clamping cylinder 61 is 
increased until the desired clamping pressure is achieved. The torquing 
cylinder 71 is then actuated to rotate the upper wrench 37 in relation to 
the lower wrench 33, thus making or breaking the connection between the 
top drive sub 29 and the tool joint 35 on the drill string 27. 
To remove the wrench assembly 31 from the connection, the lower wrench 33 
is first released. To release the lower wrench 33, the clamping cylinder 
61 retracts the die block 59 from the tool joint 35. Fluid cylinder 53 
then pivots the latch arm 43 to the open position, and fluid cylinder 51 
pivots the gate arm to the open position. The wrench assembly 31 is then 
lowered to disengage the splines 39, 67 on the top drive sub 29 and the 
top wrench 37. The wrench assembly 31 is retracted away from the 
connection, raised, and returned to its storage position beneath the top 
drive unit 19. 
The wrench assembly of the invention has several advantages over the prior 
art. Because of the various teeth 57 on the latch arm 43 which may be 
engaged by the gate arm teeth 55, the wrench assembly 31 may be used on a 
large variety of tubular members without having to be adjusted. The spline 
connection between the upper wrench 37 and the top drive sub 29 eliminates 
the need to repeatably grip the top drive sub with tong dies. Repeated 
gripping with tong dies would damage the sub 29, which must then be 
replaced. The wrench assembly 31 of the invention can be retracted away 
from the stem 25 and the drill string 27. This capability allows the 
wrench assembly 31 to remain stationary rather than to rotate with the 
drill string 27. The ability of the wrench assembly 31 to be raised to the 
storage position, shown in FIG. 1, allows the top drive drilling apparatus 
to drill the drill string to a deeper depth before additional pipe 
sections must be added to the drill string 27. 
While the invention has been shown in only one of its forms, it should be 
apparent to those skilled in the art that it is not so limited, but is 
susceptible to various changes and modifications without departing from 
the spirit thereof. For example, the wrench assembly may have an upper 
wrench of the same design as the lower wrench 33 described above.