Apparatus for guiding and steering earth boring casing

#The invention relates to apparatus for guiding and steering pipe casing to form a cased bore underground by boring and pushing the casings through a bore with an earth boring machine. In particular, the invention relates to a guidance and steering apparatus in which the direction of the pipe casing is controlled in both the vertical and horizontal planes during boring.

#Prior earth boring machines are known which are slidably mounted and reciprocated longitudinally along a track by means of a hydraulic piston assembly. The forward end of the boring machine rotatably mounts an auger which is rotated within the interior of the pipe casings with the forward end of the auger boring a hole in the earth. The auger bores the hole and carries the dirt outwardly for ejection at the boring machine. The hydraulic pistons which are forced on the boring machine to drive the pipe casings through the bore as it is formed. Successive pipe casings are attached to the string of pipe casings as the bore progresses. A steering head is typically located at the forward pipe casing and is provided with a directional control device. Typical earth boring machines are disclosed in U.S. Pat. Nos. 4,042,046, 4,013,134, and 4,438,820. U.S. Pat. No. 4,042,046 discloses an earth boring machine having a double jointed steering head so that its direction may be controlled in both the vertical and horizontal planes. However, the resulting mechanism is relatively complicated and unreliable because it involves considerably more moving parts which are at the end where the cutting occurs and considerable dynamic forces are imparted. The system does not have a reliable means for measuring the position of the cutting head in both the horizontal and vertical planes so that it may be steered accurately. U.S. Pat. Nos. 4,042,046 and 4,013,134 utilize a conventional water level to determine the grade of the casing. That type of device includes a sight tube on an indicator board at the boring pit station connected to a water line affixed to the top of the casing being bored and pushed through the ground. Any deviation in the leading edge of the casing from the desired grade either up or down provides a corresponding response to the water level in the sight tube at the boring pit. Based on the readings of the sight tube, the operator in the boring pit may pivot the steering head of the casing in the vertical plane by means of a mechanical linkage. However, the water line connected to the sight tube must be vented on both ends. If the device is used below the water table, water can enter the tube and interfere with the reading of the sight tube. The water level devices also have inherent vibration problems with necessitate that the apparatus be shut down to take a reading of the sight tube. The sight tube cannot be monitored simultaneously with the boring operation. With the vibrations, air locks are often created which interfere with the accuracy of the reading in the sight tube. The above inaccuracies can result in the final line being off grade which often requires re-boring. U.S. Pat. No. 4,438,820 proposes an improved rate sensor for eliminating the problems utilized in water level sensors. However, the problem remains that the prior art earth boring machines for cased bores do not recognize the ability to provide means for accurately measuring the position of the steering head in both the vertical and horizontal planes as opposed to being able to sense grade only. The result is that even if the grade of the cased bore is accurate, the cased bore has deviated in its horizontal position.

#In addition to the limitations of the position sensors of the prior art earth boring and casing machines, have been the problem of suitable mechanical means for pivoting the steering head relative to the casings in two degrees of freedom so that large mechanical portions are not required. Prior boring machines have utilized circular pivot flanges, such as shown in U.S. Pat. No. 4,042,046, and mechanical actuation rods affixed to the steering head which are actuated by racks assemblies to pivot the steering head. Pivot connections of the type utilized heretofore in the prior art have required large mechanical portions to move the steering head which have prevented them from being precisely controlled by small incremental forces necessary for accurate steering.

#The construction designed to carry out the invention will hereinafter be described, together with other features thereof. The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown and wherein:

#FIG. 1 is a perspective view of an earth boring machine for forming a cased bore having a guidance and steering system according to the invention;

#FIG. 2 is a top plan view of the earth boring machine of FIG. 1;

#Referring now in more detail to the drawings, an earth boring machine, designated generally as 10, is illustrated which may be any suitable machine such as a Model 36-600, horizontal earth boring machine manufactured by American Augers of Wooster, Ohio. Such earth boring machines are well known, and only those portions of a machine necessary to an understanding of the invention will be illustrated. The earth boring machine is driven by a hydraulic motor which actuates a push bar or piston (not shown) to force steel pipe casings, generally designated as 12, along a track 14 as they enter the earth and are forced through a bore which is cut up by a cutting head 16. As the cased bore is formed, the hydraulic pusher is retracted and a new casing 12 is connected to a rear casing 12a and then the new casing is pushed forward. This continues until the cased bore is completed. At the forward end of the string of casings, there is a forward casing 12b pivotally connected to a steering head, designated generally as 20. Cutting head 16 is carried by steering head 20 in a conventional manner and an auger (not shown) inside the interior of the casings 12 carries the cut materials through the casings to be injected by the boring machine 10 at the boring pit station 22.

#As can best be seen in FIGS. 2-5, hinge means for connecting steering head 20 and forward casing 12b is illustrated for rotation of the steering head about first and second orthogonal axes X and Y. There is a first hinge means A having two-degrees of freedom about the X and Y axes and a second hinge means B having two-degrees of freedom about those axes. Preferably, each hinge means includes a hinge assembly which includes a bearing mount 24, and an annular bearing 26 which surrounds an annular hub 28 of the bearing mount. A bearing hinge 30 surrounds bearing 26. A cover plate 32 covers the bearing hinge and internally encloses bearing 26 and bearing mount 24. In the illustrated embodiment, second hinge means B includes a slidable hinge assembly (FIG. 4). There is a Teflon slide bearing 34 affixed to forward casing 12b. A slide member 36 is slidably received in slide bearing 34 and includes a second pivot 38 which coincides with axis Y. Pivot 38 is pivotably connected to an arm 40 which is one piece with bearing hinge 30. In this manner, a hinge assembly is provided which has two pivots. A first pivot about the X axis and a second pivot about the Y axis. The first pivot means A may be constructed essentially as second hinge means B described above. However, first hinge means A is fixed and does not slide. For this purpose, arm 40 of first hinge means A is attached to a member 42 which is affixed to the front casing 12b by any suitable means such as welding (FIG. 2). While it is preferred that both hinge assemblies are constructed using a bearing described above, it may be possible that one of the hinge assemblies, such as A, be constructed from a ball or swivel joint. The bearing structure described above provides a very low friction bearing for pivoting of steering head 20 in the vertical plane with small mechanical forces. In this manner, small precise movements may be imparted to steering head 20 by a control motor to steer the casing according to a desired grade (vertical) and line (horizontal). Bearing 36 may be constructed from any suitable low friction material such as a suitable graphite, Teflon, or other suitable polymeric material.

#As can best be seen in FIG. 3, actuation means is connected to steering head 20 for imparting an actuation force which rotates the steering head through the first and second hinge means about the first and second axes. The actuation means includes a first actuation means, designated generally as C, and a second actuation means, designated generally as D. Preferably, each actuation means includes a drive motor 50 having a drive shaft (not shown) connected to a gear or reduction box 52 which reduces the rpm of the drive shaft. Gear box 52 has an output shaft 54 with screw threads 56 formed on a free end which are received in a threaded bore 58 of a coupling member 60. A thrust bearing 62 receives the output shaft 54 of gear reduction box 52. Coupling 60 includes a coupling shaft 64 which includes a hexagonal profile that is received in a bearing box 66 to limit rotation of coupling shaft 64. In this manner, the rotational motion 68 of output shaft 54 is translated into reciprocating linear motion in the direction shown by arrow 70. Motor 50 may be any suitable control motor such as an electric or hydraulic motor driven in incremental motions to impart precise rotational control movements. Coupling shaft 64 is connected to an actuator rod. A first actuator rod 72a is connected to a ball or swivel joint 74 affixed to steering head 20 by means of a bracket 76. A second actuator rod 72b of second actuator means D is attached to slide member 36 (FIG. 2). Thus, reciprocating linear motion of first actuator rod 72a will cause steering head 20 to be raised or lowered about horizontal axis A in a pitch motion to change the grade. Actuation of rod 72b will cause steering head 20 to pivot about pivot 38 and the Y axis to steer steering head 20 left or right in a yaw motion.