Patent Publication Number: US-7219751-B2

Title: Apparatus for guiding and steering an earth boring machine and casing assembly

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to earth boring machines that are used to bore a substantially horizontal, and longitudinally extending, hole through the earth. It also relates generally to such machines where sections of pipe casing are concomitantly pushed into the horizontal hole to create a continuous casing within the bore. More particularly, it relates to an improved apparatus for guiding and steering a forward-most section of a pipe casing such that the hole and pipe direction are controlled during the boring process, which apparatus is resistant to seizing due to the presence of earthen debris that surrounds the apparatus. 
   BACKGROUND OF THE INVENTION 
   Earth boring machines that are used to create a horizontal bore, the bore being lined with a pipe casing, are well known in the art. Earth boring machines of this type typically utilize an auger at the forward, or leading, end of the pipe casing. The auger is rotated, thereby boring a horizontally disposed hole through the earth, the auger also carrying the dirt outwardly for disposal at rearward-most portion of the boring machine. Also at the boring machine, hydraulic pistons are used to drive the pipe casings through the bore as it is formed. Successive pipe casings are then attached to the series of end-to-end pipe casings as the bore progresses. In this fashion, a continuous bore and casing is made as desired or required for the particular application. 
   In order to achieve a final bore that is on grade, however, a steering head is typically located at the forward-most pipe casing or portion thereof. The steering head can be provided with a directional control device. This is also known in the art. One such control device is disclosed in U.S. Pat. No. 4,977,967 issued to Alston et al. In that type of device, a casing extension is pivotally attached to one end of a casing section and is controlled by an elongate tube that is movable along an axis that is generally parallel to the axis of the casing in order to pivot the casing extension upwardly or downwardly. A first connector for connecting one end of the tube to the casing extension and a second connector assembly connected to the other end of the tube for moving the tube and pivoting the casing extension is provided. 
   In the experience of this inventor, one difficulty encountered with the utilization of a steering head as described above is that a reversal of the steering head during the boring process tends to deposit earth into the drive mechanism, which is a threaded screw mechanism. The presence of earthen debris about the drive mechanism can cause the mechanism to seize when the boring head is re-activated to move forwardly. When this happens, the steering head mechanism will be inoperative, bring the boring process to a halt until the steering head mechanism can be cleaned or replaced. In the process of boring, cleaning of the steering head mechanism can create unacceptable down time. And if the steering head mechanism needs to be replaced, this creates unacceptable and unnecessary expense. 
   What is needed is a steering head mechanism that can be used with an earth boring machine such that the earth boring machine can be periodically reversed without causing the steering head mechanism to seize. What is also needed is such a steering head mechanism that is relatively easy and inexpensive to manufacture and which can be used in the same manner as current steering head mechanisms are used. 
   SUMMARY OF THE INVENTION 
   Accordingly, a primary objective of the device of the present invention is to provide a new, useful and heretofore unobvious steering head mechanism that can be used with an earth boring machine such that the earth boring machine can be periodically reversed without causing the steering head mechanism to seize during operation. A second objective is to provide such a steering head mechanism that is comprised of a minimum number of parts, thus making it relatively easy and inexpensive to manufacture. Another objective is to provide such a steering head mechanism that requires a minimum number of steps to use and which can be used in essentially the same manner, and in the same environment, as current steering head mechanisms are used. 
   In accordance with the aforementioned objectives of the present invention, there is provided a head steering mechanism that comprises a forward pivot block and a rearward pivot block. The forward pivot block is attached to a leading edge of a casing and the rearward pivot block is attached to a trailing portion of the casing, the leading edge being separately from the trailing portion and being horizontally adjustable relative to it. Extending between the forward and rearward pivot blocks is a central drive shaft. The central drive shaft includes a threaded portion and is rotatable so as to be able to move a drive nut in a longitudinal direction away from or towards the rearward pivot block. The threaded portion of the central drive shaft, to either side of the drive nut, is covered by a cylindrical sleeve. Another internal sleeve extends between the rearward pivot block and the drive nut to protect the threads of the drive shaft regardless of whether the mechanism is being advanced or reversed to steer the forward-most casing portion during operation. In this fashion, earthen debris is prevented from contact with the threaded drive shaft, thus allowing the steering head mechanism to operate reliably in both directions and without the possibility of causing the mechanism to seize. 
   The foregoing and other features of the apparatus of the present invention will be apparent from the detailed description that follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view of a boring machine using the improved steering head mechanism of the present invention as attached to the foreward-most portion of a casing. 
       FIG. 2  is a top plan view taken along line  2 — 2  of  FIG. 1 . 
       FIG. 3  is an enlarged side elevational view of the foreward-most casing portion with the steering head mechanism attached to it. 
       FIG. 4  is a further enlarged and partially sectioned side elevational view of the steering head mechanism of the present invention. 
       FIG. 5  is a partially sectioned top plan view of the steering head mechanism shown in  FIG. 4 . 
       FIG. 6  is another partially sectioned side elevational view of the steering head mechanism shown in  FIG. 4  and illustrating the mechanism in a second position. 
       FIG. 7  is a greatly enlarged view taken along arcuate line  7 — 7  of  FIG. 6  and showing detail of the cooperating sleeves used in the mechanism. 
       FIG. 8  is a rear, side and top perspective view of the steering mechanism constructed in accordance with the present invention. 
   

   DETAILED DESCRIPTION 
   Referring now to the drawings in detail, wherein like numbered elements refer to like elements throughout,  FIGS. 1 and 2  illustrate a steering head mechanism, generally identified  100 , constructed in accordance with the present invention. As shown, the steering head mechanism  100  is utilized with a boring machine  300  and its related components that are used for cutting a bore  410  into the earth  400 . 
   More specifically, it will be seen that the steering head mechanism  100  is attached to the foremost portion  210  of a longitudinally extending casing  200 . The casing  200  is an elongate hollow pipe casing of conventional type and length that projects into the bore  410  within the earth  400 . Forward of the casing  200  is an auger bore head  310 . An auger  320  is rotated within the casing  200  to move debris through the casing  200  as it is loosened by the bore head  310 . The auger  320  and bore head  310  are rotatably driven by the boring machine  300  which is located at the opening  420  of the bore  410 . It is to be understood that the precise type of boring machine  300  that can be used with the device of the present invention is not a limitation of the present invention. It is also to be understood that the device of the present invention is not limited to use with a single casing  200  and that, after the casing  200  is inserted into the bore  410 , a second casing  200  will be attached to it and an additional auger  320  section will be added, and so on to the point that multiple casings  200  and auger sections  320  are used until the desired or required length of the bore  410  is reached and the bore  410  is completed. 
   Referring now to  FIG. 8  which illustrates the steering head  100  in an unattached state, it will be seen that the steering head mechanism  100  includes a forward pivot block  10  and a rearward pivot block  20 . See also  FIG. 4 . The forward pivot block  10  is comprised of a pair of parallel block plates  12 , each block plate  12  being fabricated of a metal material. In the steering head  100  of the present invention, the block plates  12  are positioned parallel planar to one another. See also  FIG. 5 . Each forward pivot block plate  12  includes a tapered leading edge  14  and a flat foot portion  16 . This tapered leading edge  14  facilitates movement of the head  100  through the earth  400  and along the bore  410 . The foot portion  16  of each plate  12  is located generally parallel to the outer surface of the main casing  200 , which casing  200  is typically made of a cylindrical metal material. Accordingly, attachment of the plate  12  to the casing  200  is best accomplished by welding. In particular, the foot portion  16  of each plate  12  is functionally adapted to be attached, generally perpendicularly, to the short forward-most casing piece  210  of the main casing  200 . Each plate  12  of the forward pivot block  10  also includes a generally perpendicular aperture  18  defined within the plate  12 . The apertures  18  of the plates  12  are co-linear along their respective axes in order to accommodate placement of a rod-like retention device through them, as will be discussed later in this detailed description. 
   Referring again to  FIG. 8 , it will be seen that the rearward pivot block  20  includes a pair of rearward pivot block plates  22 , each of which is parallel planar to the other and each of which is preferably fabricated of metal material. See also  FIGS. 4 and 5 . Each plate  22  includes a foot portion  24  and a generally perpendicular aperture  26 . The apertures  26  of the plates  22  are co-linear. The foot portions  24  of the plates  22  of the rearward pivot block  20  are functionally adapted to be attached, generally perpendicularly, to a rearward portion of the casing  200 , preferably by welding. 
   Referring now to the detail shown in  FIG. 3 , it will be seen that a casing slit or gap  214  separates the rearward main portion of the casing  200  and a short forward-most casing piece  210 . This slit or gap  214  is really a partial “cut-through” in the casing  200  which connects the rearward portion of the casing  200  and the short casing piece  210  by means of a connector  216  that is opposed 180° relative to the position of the steering head  100 . The purpose and advantage of this connector  216  will be further apparent later in this detailed description. It is the short casing piece  210  that the forward pivot block  10  is attached to in the preferred embodiment. It is to be understood, however, that the short casing piece  210  and the main casing  200  could be connected by other means that would provide flexing between those two components. 
   Referring again to  FIGS. 4 ,  5  and  8 , it will be seen that, disposed between the parallel planar plates  12  of the forward pivot block  10 , there is located a cylindrically shaped, and substantially solid, first pivot block member  60 . This pivot block member  60  is, in the preferred embodiment, a cylindrically shaped piece of metal material that is rotatably secured between the plates  12  by means of a pivot block pin  62 . The pin  62  is insertable through the plate apertures  18  and welded  68  at each end to secure it in place. The first pivot block member  60  further includes a rearward portion  64 . It should also be noted here that, in the preferred embodiment, close tolerances are to be followed to allow for proper movement and rotation of the various elements in relation to each other and to prevent earthen debris from working its way into and between those elements. 
   Disposed between the parallel planar plates  22  of the rearward pivot block  20  is a second pivot block member  40 . The rearward second pivot block member  40  is rotatably attached to the plates  22  by means of a pair of opposing block keeps  42 , each of which is disposed to either side of the block member  40 . The second pivot block member  40  also includes a forward flat  44 , a rearward flat  46 , and a centrally disposed aperture  48 . The purpose and function of each of these elements will become apparent later in this detailed description. 
   The steering head mechanism  100  of the present invention also includes a longitudinally extending central drive shaft  30  having a forward portion  32  and a rearward portion  34 . See  FIGS. 4 and 5 . The forward portion  32  of the central drive shaft  30  is threaded. In the preferred embodiment, the central drive shaft  30  is fabricated of a metal material with the threads of the threaded forward portion  32  being ACME threads. The rearward portion  34  of the central drive shaft  30  is configured in a substantially hexagonal cross section such that the rearward portion  34  can be driven by a female hexagonal member  315 , as shown in  FIG. 1 . The rearward portion  34  of the central drive shaft  30  further includes a ring  36  that is secured by weldment  38  at the rearward most threaded portion  34  of the central drive shaft  30 . The ring  36  is provided to prevent the passage of earthen debris into the threaded portion  32  of the drive shaft  30 . The presence of the ring  36  also prevents forward movement of the central drive shaft  30  as the hexagonally shaped rearward portion  34  is rotated, thereby rotating the central drive shaft  30  about its axis during normal operation of the steering head mechanism  100 . A portion of the central drive shaft  30  extends through the rearward block aperture  48  as alluded to earlier and as is shown in  FIGS. 4 ,  5  and  6 . 
   The forward portion  32  of the central drive shaft  30  also extends through a threaded drive nut  50 . In the preferred embodiment, the drive nut  50  includes a forward shoulder  52  and a rearward shoulder  54 . See  FIGS. 4 and 5 . In the steering head mechanism  100  of the present invention, it is important that each shoulder  52 ,  54  be machined into the drive nut  50  to form a circular surface to either side of the nut  50 . The reason for this is that each shoulder  52 ,  54  is provided to allow a pair of outer sleeves  80 ,  90  to be secured to the nut  50 , as will be explained shortly. 
   Extending between the forward most portion  44  of the rearward pivot block member  40  and the drive nut  50  is an inner sleeve  70  that surrounds the central drive shaft  30 . In the preferred embodiment, the inner sleeve  70  is a cylinder made of a metal material. The inner sleeve  70  has a forward end  72  and a rearward end  74 . The forward end  72  of the inner sleeve  70  is welded  76  to the central drive shaft  30  at a point that is just behind the rearward facing surface  56  of the drive nut  50 . The position of the weld  76  is according to a predetermined distance of the drive nut  50  from the second pivot block member  40 , which distance coincides with the length of the inner sleeve  70 . The rearward end  74  of the inner sleeve  70  abuts the front face  44  of the rearward pivot block member  40  and is rotatably movable in respect to it. In this fashion, that portion of the drive shaft  30  which is threaded and which lies beneath the inner sleeve  70  is completely protected from its working environment. 
   Extending in the same fashion between the drive nut  50  and the rearward pivot block member  40  is a first outer sleeve  80 . The first outer sleeve  80  is a cylinder, of slightly greater diameter than that of the inner sleeve  70 , and is made of a metal material. The first outer sleeve  80  includes a forward end  82  and a rearward end  84 . The forward end  82  of the first outer sleeve  80  is welded  86  about its perimeter to the rearward facing drive nut shoulder  54 . In this fashion, the first outer sleeve  80 , including the rearward end  84  of it, is able to slide in extremely close tolerance along the inner sleeve  70 . This is shown by the letters and dimension CL in  FIG. 7 . It is to be understood that the inner diameter of the first outer sleeve  80  closely approximates the outer diameter of the inner sleeve  70  so as to prevent the entry of earthen debris between those two cooperating parts. In the preferred embodiment, the rearward end  82  of the first outer sleeve  80  is chamfered  88  to allow that end  82  to move easily through earthen debris when the first outer sleeve  80  is moved backwardly over the inner sleeve  70 . Although not shown, a brush or seal could be interposed between the inner sleeve  70  and the first outer sleeve  80  in order to facilitate the resistance of debris penetration between those two component parts. 
   Disposed between the drive nut  50  and the rearward portion  64  of the forward pivot block member  60  is a second outer sleeve  90 , the second outer sleeve  90  being a cylinder of substantially the same diameter as the first outer sleeve  80  and being made of a metal material. The second outer sleeve  90  similarly includes a forward end  92  and a rearward end  94 . The rearward end  94  of the second outer sleeve  90  is secured, preferably by welding  96  about its perimeter, to the forward facing drive nut shoulder  52 . The forward end  92  of the second outer sleeve  90  is similarly welded  98  about its perimeter to the rearward portion  64  of the first pivot block member  60 . In this fashion, the threaded portion  32  of the central drive shaft  30  that lies beneath the second outer sleeve  90  is completely protected from earthen debris. 
   In application, the forward pivot block plates  12  of the steering head mechanism  100  are welded to a forward-most portion  210  of a main casing  200 . The boring head  310  is located at this forward-most portion  210 . As dirt and earth are loosened at the auger  320 , this debris is passed through the casing  200  and discarded. It will be recalled that the rearward pivot block plates  22  of the mechanism  100  are similarly welded to the main casing  200  at some point behind the casing slit  214 . 
   At some point during the boring process, it may be necessary to change the pitch of the axis of the bore  410  either upwardly or downwardly, as required. Due to the weldment positions of the forward pivot block  10  and the rearward pivot block  20 , the axis of the forward-most portion  210  of the main casing  200  and the axis of the main casing can be varied by lengthening the distance between the forward and rearward pivot blocks  10 ,  20  or by shortening that distance. This, in turn, affects the width of the slit or gap  214 . If the distance is lengthened, and the width of the slit or gap  214  at the point of the steering head mechanism  100  is enlarged, then the forward-most portion  210  will begin a descent of the casing  200 , whereas a shortening will begin an ascent of the casing  200 . See  FIG. 3 . A lengthening of that distance will occur when the rearward hexagonal portion  34  of the central drive shaft  30  is rotated, for example, clockwise. This clockwise rotation, in turn, causes the drive nut  50  to move away from the rearward pivot block  20  and taking with it the first and second outer sleeves  80 ,  90  that are welded to it. This action also allows the first outer sleeve  80  to slide over the outer surface of the inner sleeve  70 , thereby exposing the inner sleeve  70  to earthen debris but not exposing the threaded portion  32  of the central drive shaft  30 . 
   If, during the boring process, it becomes necessary to reverse the rotation of the central drive shaft  30 , this moves the forward pivot block  10  towards the rear pivot block  20  and reverses the direction of travel of the drive nut  50 . This also causes the first outer sleeve  80  to slide back over the inner sleeve  70  towards the rear pivot block  20 . Any earthen debris that is in contact with the inner sleeve  70  is gently urged away from the inner sleeve  70  outer surface  78  by means of the chamfered end  88 , thus allowing the mechanism  100  to be reversed and the direction of travel of the auger  300  and casing  200  to be altered relative to the horizontal. By keeping earthen debris away from the threaded surface  32  of the drive shaft  30  and the drive nut  50 , there is no chance of the mechanism  100  seizing during normal operation due to the presence of that debris within the device. 
   Although the foregoing has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made by way of example only and that numerous changes in the construction and the arrangement of components, some of which have been alluded to, may be resorted to without departing from the spirit and scope of the invention as it is described. 
   From the foregoing detailed description of the illustrative embodiment of the invention set forth herein, it will be apparent that there has been provided a new, useful and uncomplicated steering head mechanism that can be used with an earth boring machine such that the earth boring machine can be periodically reversed without causing the steering head mechanism to seize during operation; that is comprised of a minimum number of parts, thus making it relatively easy and inexpensive to manufacture; and that requires a minimum number of steps to use and which can be used in essentially the same manner, and in the same environment, as current steering head mechanisms are used.