Self-propelled drilling head

A self-propelled drilling head comprises a base section including gripper shoes mounted for extension and retraction to selectively grip the wall of a hole being drilled. A first actuator is provided for extending and retracting the gripper shoes. A drilling section is mounted on the base for reciprocation relative thereto. A second actuator is provided for urging the drilling section downwardly relative to the base section when the gripper shoes are extended. A cutter bit is mounted at a lower end of the drilling section. A third actuator is provided for rotating the cutter bit and comprises a first hydraulic motor having a first output shaft. A second hydraulic motor is spaced below and laterally offset from the first hydraulic motor and has a second output shaft extending parallel to the first output shaft. A driven gear is mounted at the end of each output shaft. A drive transmitting gear mechanism is meshingly engaged on opposite sides by the driven gears. A first conduit supplies pressurized hydraulic fluid to the first and second motors. A second conduit conducts hydraulic fluid from the first and second motors. A power transmitting mechanism operably connects the drive transmitting gear to the cutter bit to rotate the latter.

BACKGROUND AND OBJECTS OF THE INVENTION 
The present invention relates to a drill for use in oil and gas drilling 
operations. 
Drills have been proposed for gas and oil drilling which comprise 
multi-sectioned drill strings extending from the ground surface and 
carrying a cutter bit at the lower end. Rotary drive forces are applied to 
the drill string at the ground surface and are transmitted along the drill 
string to rotate the cutter bit. Not only are relatively large 
expenditures of energy required to rotate the entire drill string, but it 
is necessary to raise and uncouple every section of drill string in order 
to periodically replace the cutter bit. Furthermore, in the event that a 
break occurs along the length of the drill string, it is very difficult, 
if not impossible, to retrieve the string. 
It has been heretofore proposed to eliminate the need for a drill string by 
utilizing a self-propelled cutter head which drills into the ground by 
means of a cutter head driven by a power plant carried by the head. The 
cutter head may comprise a plurality of telescoping sections, each 
carrying extensible/retractible shoes for engaging the wall of the hole 
being drilled. In this manner, one of the telescoping sections can be held 
fixed while the other section extends or retracts, and vice-versa, to 
enable the cutter head to "walk" down the hole in order to power the 
cutter bit. The power plant powers the cutter bit and is supplied with 
energy from the surface, such as electrical power or pressurized fluid, 
for example. Examples of such self-propelled heads are disclosed in U.S. 
Pat. No. 2,473,537 issued June 21, 1949; U.S. Pat. No. 2,643,087 issued 
June 23, 1953; U.S. Pat. No. 3,173,501 issued Mar. 16, 1965; U.S. Pat. No. 
3,185,225 issued May 25, 1965; U.S. Pat. No. 3,232,362 issued Feb. 1, 
1966; U.S. Pat. No. 3,407,887 issued Oct. 29, 1968; U.S. Pat. No. 
3,882,946 issued May 13, 1975; U.S. Pat. No. 4,060,141 issued Nov. 29, 
1977; and U.S. Pat. No. 4,143,722 issued Mar. 13, 1979. 
Among the difficulties connected with the utilization of such 
self-propelled cutting heads is the need to dispose a practicable 
high-energy power plant within the limited amount of space available on 
the cutter head. Various proposals in this area involve the use of a drive 
mechanism disposed coaxially within the head, such as large turbine, a 
large hydraulic motor, or a group of series-connected electric motors, for 
example. While electrical power is simpler to supply than other forms of 
energy, it presents a serious heat dissipation problem within the drilling 
head. Fluid-actuated mechanisms such as turbines and hydraulic motors 
require that provision be made for supplying and withdrawing a continuous 
flow of pressurized fluid, thereby complicating the efforts to simplify 
and streamline the apparatus. 
The use of a large coaxial fluid actuated mechanism maximizes the 
cross-sectional dimension of the drilling head, thereby further hindering 
streamlining efforts and, in the case of turbines, complicating the 
ability to conduct the spent hydraulic fluid upwardly from the bottom of 
the turbine. 
It is, therefore, an object of the present invention to minimize or obviate 
problems of the type discussed above. 
Another object of the invention is to provide a self-propelled drilling 
head which is of minimal cross-sectional dimension. 
It is an additional object of the invention to provide a powerful 
space-saving drive mechanism for the cutter bit. 
It is yet another object of the invention to provide an efficient drive 
train for transferring power efficiently and smoothly from the drive 
motors to the cutter bit. 
It is a further object of the invention to provide a self-propelled 
drilling head of the step-down type which employs hydraulic fluid and 
effectively supplies and returns hydraulic fluid through the head by 
conduits which occupy minimal space. 
A further object of the invention is to provide a self-propelled cutter 
head in which the components are safely shielded within rigid housings. 
SUMMARY OF THE INVENTION 
These objects are achieved by the present invention which relates to a 
self-propelled drilling head. The drilling head comprises a base section 
including gripper shoes mounted for extension and retraction to 
selectively grip the wall of a hole being drilled. A first actuator is 
provided for extending and retracting the gripper shoes. A drilling 
section is mounted on the base for reciprocation relative thereto. A 
second actuator is provided for urging the drilling section downwardly 
relative to the base section when the gripper shoes are extended. A cutter 
bit is mounted at a lower end of the drilling section. A third actuator is 
provided for rotating the cutter bit and comprises a first hydraulic motor 
having a first output shaft. A second hydraulic motor is spaced below and 
laterally offset from the first hydraulic motor and has a second output 
shaft extending parallel to the first output shaft. A driven gear is 
mounted at the end of each output shaft. A drive transmitting gear 
mechanism is meshingly engaged on opposite sides by the driven gears. A 
first conduit supplies pressurized hydraulic fluid to the first and second 
motors. A second conduit conducts hydraulic fluid from the first and 
second motors. A power transmitting mechanism operably connects the drive 
transmitting gear to the cutter bit to rotate the latter.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
In FIG. 1 there is depicted a self-propelled cutter head 10 according to 
the present invention as it penetrates downwardly through a formation by 
means of a suitable cutter bit 12 carried at a lower end of the head 10. 
The head 10 includes a base section 14, and a drilling section 16 
telescopingly carried by the base section for reciprocation relative 
thereto under the influence of a reciprocating fluid motor. A 
fluid-actuated drive mechanism 18 (FIG. 4c) is carried by the drilling 
section for rotating the drill bit 12. The base and drilling sections 14, 
16 carry laterally extensible/retractible, vertically elongate shoes 20, 
22 which when extended grip the wall of the hole being drilled. When the 
shoes of either of the sections 14, 16 are extended against the wall, the 
shoes of the other section are retracted, whereby the latter section is 
free to travel relative to the former section. In this way, the head is 
able to "walk" down the formation. 
The base section 14 comprises an outer-cylindrical housing 24, the lower 
end of which is open to receive the upper end 26 of the drilling section 
16. Mounted on the housing 24 are the extendible/retractible shoes 20. 
Preferably, there are two arc-shaped shoes 20, each being mounted by pairs 
of upper and lower links 28, 30 (FIG. 4b). The upper links 28 are of 
triangular shape and are each pivotably connected at 32 to a bracket on 
the housing 24 and at 34 to a bracket on the shoe 20. The lower links 30 
are pivotably connected at 36 to a bracket on the housing and at 38 to a 
bracket on the shoe 20. The links 28, 30 function as a parallelogram 
linkage which is actuated by hydraulic rams 40. Each hydraulic ram 40 
(FIG. 5) comprises a cylinder 42 and a pair of reciprocable piston/rod 
assemblies 44. The outer ends of the rods are pivotably connected at 46 to 
the upper links 28 and are operable to extend the shoes outwardly against 
the formation when the center or piston section 48 of the ram chamber is 
pressurized, and retract the shoes away from the formation when the end or 
rod sections 50 of the ram chamber are pressurized. Since each ram 40 is 
mounted to the base section only by virtue of its rod ends being connected 
to the links 28, the ram is adapted to rise and fall as the link 28 is 
swung inwardly and outwardly, i.e., the ram adapts to the level of the 
pivots 46. 
Pressurized fluid for actuating the rams 40 is delivered by a pressurized 
fluid conduit 52 which communicates with the rams 40 by inlet lines 54 and 
valves 55, 56. Return fluid is conducted through the valves 55, 56, outlet 
lines 58 and a fluid return conduit 60. The valves 55, 56 are conventional 
electrical solenoid actuated valves which are powered by electrical 
connection with at least one electrical conductor 59. The conduits 52, 60 
and the conductor 59 pass completely through the housing 24 and extend 
into the drilling section 16. 
Connected to the top of the housing 24 is a tubular drill crown 62 which is 
preferably formed of braided metal strands and which surrounds the 
conduits 52, 60 and the conductor 59. Cables (not shown) are connected to 
the top of the drill crown to support the tool and enable recovery thereof 
at the end of a drilling operation. Slots 61 are formed in the drill crown 
through the rams 40 project. 
The upper end 26 of the drilling section is slidable within the housing 24 
and carries outer seals 63 and inner seals 64. There is thus defined a 
chamber 65 above a top wall 66 of the drilling section 16 into which 
pressurized fluid may be introduced in order to impart a downward thrust 
to the drilling section 16. The upper portion 26 of the latter thus 
defines a piston against which the pressurized fluid acts. Pressurized 
fluid is introduced into the chamber 65 through an inlet valve 67 
communicating with the fluid supply conduit 52. The base section 14 is 
permitted to descend by gravity by communicating the chamber 65 with the 
fluid return conduit 60 via an exhaust valve 68. Electric power for 
actuating the valves 65, 66 is supplied by the conductor 59. If desired, 
the upper portion 26 of the drilling section 16 can be formed as a two-way 
piston so that the base section 14 would be pulled downwardly. 
The upper end 26 of the drilling section is rotatably mounted in a 
cylindrical casing 70 of the drilling section by means of a rotary thrust 
and self-aligning bearing 72 (FIG. 4c). Mounted on the casing 70 are four 
pairs of vertically spaced hydraulic rams 74 which each include a cylinder 
76 and piston/rod assemblies 78. Four lower shoes 22 are carried at the 
outer ends of the piston/rod assemblies (FIG. 6). 
Pressurized fluid for actuating the rams 74 is supplied by the fluid 
delivery conduit 52 which communicates with a series of electrical 
solenoid-actuated valves 80, 82, 83. The valves are connected to the 
conductor 59 and are actuable to cause simultaneous extension or 
retraction of the lower shoes 22. 
Disposed beneath the rams 74 is the drive mechanism 18 for the cutter bit 
12. The drive mechanism comprises a drill bit hub 90 which projects from 
the drilling section 16 and has external screw threads for threadedly 
connecting to the cutter bit. The drill bit hub 90 is rotatably mounted in 
rotary and thrust bearings 92, 94 carried by the casing 70. 
Extending upwardly from the drive shaft and connected for rotation 
therewith is a ring gear 96 (FIGS. 4c, 10). The ring gear has internal 
teeth 97 meshing with four secondary drive gears 100, the latter being 
carried out on vertical rotary axles 101. 
A primary drive gear 102 meshes centrally with the secondary drive gears 
100 and is mounted on a vertical shaft 106. The primary and secondary 
gears are thus arranged in sun-planet relationship. The shaft 106 carries 
a pinion gear 108 above the main drive gear 104. Opposite sides of the 
pinion gear 108 mesh with a pair of driven gears 110, 112, the latter 
being fixed at the ends of laterally spaced vertical output shafts 114, 
116 of a pair of laterally and vertically spaced hydraulic fluid motors 
118, 120 disposed in laterally overlapping relationship (FIGS. 4c, 7, 8). 
Each motor 118, 120 comprises a conventional hydraulic motor containing 
intermeshing toothed wheels 122, 124 disposed within a chamber 126. 
Pressurized fluid is supplied to the chamber from a branch 52C, 52D of the 
fluid delivery conduit and removed therefrom through a branch 60C, 60D of 
the fluid return conduit. The pressurized fluid drives wheels 122, 124 of 
the motors 118, 120, thereby turning the output shafts 114, 116 which are 
fixedly connected thereto. The other wheels 126, 128 are connected to 
idler shafts 130, 132. 
It will be appreciated that the driven gears 110, 112 engage opposite sides 
of the pinion 108 and thus provide an efficient balanced application of 
force thereto. The hydraulic motors 118, 120 are relatively compactly 
arranged and yet in combination represents a powerful source of energy. 
The motors are spaced and staggered and are thus adaptable to slim 
profiles of the drilling head. 
Power is transmitted by the pinion gear 108 to the primary drive gear 104 
by the shaft 106, and by the primary drive gear to the secondary drive 
gears 100. The secondary drive gears rotate the ring gear 96 which, in 
turn, drives the cutter bit hub 90. Accordingly, the driven cutter bit 
chips away the formation as the drilling section 16 is pushed downwardly 
relative to the base section 14, the latter being held against stationary 
by the upper shoes 20. At the end of a cutting stroke of the drilling 
head, the upper shoes 20 are retracted and the lower shoes 22 are extended 
(if necessary) to enable the base section to descend by gravity relative 
to the drilling section. 
In order to adapt the hydraulic supply and return conduits and the electric 
conductor 59 to the telescoping action of the base and drilling sections 
14, 16, those conduits and conductor are rendered extensible and 
retractible within the drilling head by an arrangement comprising 
telescoping tubes. That is, the hydraulic supply conduit 52 comprises 
upper and lower telescoping tubes 52A, 52B (FIG. 4b), the latter being 
telescopingly received within the former. Seal rings 160 form a seal 
between the segments 52A, 52B to assure that all fluid is constrained to 
flow from the upper tube 52A into the lower tube 52B. The hydraulic return 
conduit 60 is similarly defined by telescoping tubes 60A, 60B. The 
conductor 59 includes a slip ring assembly 162 which enables portions 164, 
166 of the conductor 59 to slide relative to one another while maintaining 
a continuous electrical supply. Thus, as the base and drill sections 14, 
16 travel relative to one another, the tubes 52A, B and the conductor 
portions 164, 166 telescope relative to one another to automatically 
adjust to a proper length. 
In operation, the drilling head performs a drilling stroke while the upper 
shoes 20 are extended against the wall of the hole and the lower shoes 22 
are retracted (FIG. 3). During this stroke, pressurized hydraulic fluid is 
introduced into the chamber 65 in order to continuously urge the drilling 
section 16 downwardly relative to the base section 14. The formation is 
chipped away by the cutter bit 12 which is driven by the hydraulic motors 
118, 120. Pressurized fluid is delivered to those motors from the fluid 
supply conduit 52 and is removed by the fluid return conduit 60 (FIGS. 7, 
8). The parallel output shafts 114, 116 power the driven gears 110, 112 
which drive opposite ends of the pinion 108. Motion is transmitted by the 
pinion 108 to the sun or primary drive gear 104 through the spindle 106. 
The primary drive gear drives the planet or secondary drive gears 100. The 
latter rotates the ring gear 96 which powers the cutter bit shaft 90. 
At the end of a drilling stroke, when the drilling section 16 lies fully 
extended, the upper shoes 20 are retracted and, if desired, the lower 
shoes 22 are extended (FIG. 2). Then, the chamber 65 is communicated with 
the fluid return conduit 60, allowing the base section 14 to gravitate 
downwardly relative to the drilling section 16. Accordingly, the drilling 
head is positioned for a subsequent drilling stroke. 
During relative movement between the base and drilling sections 14, 16, the 
telescopic tubes 52A, 52B and 60A, 60B of the fluid supply and return 
conduits extend and retract to automatically adjust to the proper length. 
Drilling mud for the removal of cuttings can be supplied by a suitable 
conduit disposed externally of the drilling head and attached thereto. The 
drilling mud would be circulated upwardly through the annulus in a 
conventional manner. 
It will be appreciated that the hydraulic conduits are to be payed-out from 
a conventional apparatus at the surface. The conduits, which are flexible, 
are reel-mounted and are gradually payed-out while simultaneously 
conducting pressurized fluid. 
MODIFICATION 
In lieu of providing a telescoping arrangement for the fluid and electrical 
supply conduits, a modified embodiment can be employed as depicted in FIG. 
11. In that embodiment, a cylindrical housing 24A includes upper and lower 
end walls 200, 202 which are threadedly connected to the upper and lower 
ends of the housing 24A. Slidably mounted within the end walls 200, 202 is 
an upper end 26A of a drilling section 16A which is similar to that 
disclosed in connection with the earlier figures. 
The housing 24A is suspended by means of a cylindrical crown 209 which may 
be formed of braided metallic strands. 
Mounted on the upper end 26 of the drilling section is a ring 208 through 
which extend the upper ends of hydraulic conduits 210, 212, 214, 216 and 
one or more electrical cables 218. These conduits and cables are slidable 
within the upper end wall 200 and interconnect with the lower ends of 
corresponding flexible conduits and cables 210A, 212A, 214A, 216A, 218A 
which extend to the ground surface. The ring 208 is slidably mounted 
within a slot 211 in the crown 209; this prevents rotation of the upper 
end of the drilling section 16A. 
Also mounted on the upper end 26A of the drilling section 16A is a piston 
220. The piston 220 is slidable within a chamber 222 defined by the 
cylindrical housing 24A and the end walls 200, 202. The upper and lower 
end walls are suitably provided with seals 223 to assure that the chamber 
222 is leak-proof. The lower end of the conduit 210 extends completely 
through the piston 220 and communicates with the chamber 222 beneath the 
piston 220. The lower end of the hydraulic conduit 212 includes an outlet 
224 communicating with the chamber 222 above the piston. 
Provided in the upper end wall 200 are a plurality of bores 226 in which 
rams 228 are slidably mounted. Inner ends of the bores 226 communicate 
with the portion of the chamber 222 disposed above the piston 220, by 
passages 230. Conduits 232 communicate outer ends of the bores 226 with 
the portion of the chamber 222 disposed below the piston 220. 
Connected to outer ends of the rams 228 are arc-shaped shoes 20A. The shoes 
contain slots 234 within which enlarged heads 236 of the pistons slide. 
The lower ends of the shoes are connected to the housing 24A by means of 
links 238. When the rams 228 are extended, the shoes 20A are extended, the 
heads 236 sliding within the slots 234. 
In operation, pressurized hydraulic fluid conducted through the conduit 212 
communicates with the chamber 222 above the piston 220 and simultaneously 
communicates with the rams 228 via passages 230. Since the outward 
extension of the shoes 20A offers less resistance than the downward thrust 
of the piston 220 (the latter serving to push the cutter bit into the 
formation), the shoes 20A will be extended to grip the side of the 
formation. Thereafter, the piston 220 will be forced downwardly during a 
cutting stroke. As the piston 220 and rams 228 are displaced, hydraulic 
fluid is exhausted via the passages 232 and the conduit 210. As the piston 
220 travels downwardly, the ring 208 slides within the slot 250 in the 
crown 209. Simultaneously, the hydraulic conduits 210A, 212A, 214A, 216A, 
218A are payed-out from the surface. Hydraulic flow is reversed when it is 
desired to retract the pistons and lower the housing 24A. 
It will be appreciated that the present invention provides a self-propelled 
drilling head which exhibits ample power and yet can be formed of slim 
profile due to the spaced and staggered arrangement of plural hydraulic 
drive motors. The output shafts of the motors power opposite sides of a 
pinion gear to effect a highly efficient and balanced transfer of power 
from the drive mechanism. The arrangement of sun and planet gears which 
drive a ring gear assures a smooth and effective transfer of power to the 
cutter bit. The use of telescoping fluid conduits and electrical conductor 
minimizes space while presenting minimum chance that such elements will be 
fouled as the step-down mechanism operates. All components of the drilling 
head are protected within closed housings, and the fluid conduits and 
electrical connector are shielded within the support cable. 
Although the invention has been described in connection with a preferred 
embodiment thereof, it will be appreciated by those skilled in the art, 
that additions, modifications, substitutions and deletions not 
specifically described, may be made without departing from the spirit or 
scope of the invention as defined in the appended claims.