Abstract:
An anchor assembly for securing a boring machine to the earth is provided. The anchor assembly includes a shaft equipped with a helical assembly by which the shaft can be driven into and removed from the earth like a screw. The helical assembly preferably includes a plurality of flights and a plurality of wings pivotally attached to the flights and helically aligned therewith. The wings and flights are configured so that rotation in one direction urges the wings into the retracted position. However, counter-rotation for only part of a turn forces the wings into the extended position, which expands the diameter of the helical assembly. Thus, the extended wings bite into soil that was undisturbed during the initial insertion, providing increased frictional engagement between the anchor and the soil. Yet, because the wings are helically aligned with the flights, the extended wings do not substantially resist withdrawal of the anchor assembly from soil by reverse rotation. The anchor assembly includes a cap assembly with a cylindrical skirt that engages the surface of the earth around the anchor insertion point. A lock nut presses the skirt into the ground clamping the soil between the plate and the helical assembly giving even greater strength to the engagement between the anchor assembly and the earth. The large vertical surface area provided by the skirt, in conjunction with the “ground-clamping” action of the cap assembly, aids in restricting lateral movement of the boring machine and resisting premature displacement of the anchors.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an anchor assembly for securing an object to a compressible material, and more particularly to an anchor assembly for securing a boring machine to the earth adjacent the boring site. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an anchor assembly for securing an object to a compressible material. The anchor assembly comprises a shaft having an upper and a lower portion and a helical assembly on the lower portion of the shaft. The helical assembly comprises a helical flight that renders the lower portion insertable into the compressible material by rotating the shaft in a first direction and axially advancing the shaft. The lower portion of the shaft is also thereby rendered removable from the compressible material by rotating the shaft in a second direction opposite the first direction and axially withdrawing the shaft. The helical assembly also includes a wing supported adjacent the lower portion of the shaft and movable between an extended position and a retracted position. The wing is helically aligned with the helical flight in both the extended position and the retracted position. The wing is connected so that, as the shaft is inserted into the compressible material, the wing is urged toward the retracted position. Likewise, as the shaft is rotated in the second direction, the wing is urged toward the extended position thereby expanding the outer diameter of the helical assembly. 
     Further, the present invention is directed to a boring machine comprising a frame and some means for advancing a drill string from the frame to form a borehole in the earth. The boring machine is equipped with the anchor assembly described above. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a boring machine anchored in the earth using anchor assemblies in accordance with the present invention. 
     FIG. 2 shows a side elevational, partly sectional view of an anchor assembly partially embedded in the earth. 
     FIG. 3 is a side elevational view of the upper portion of the shaft of the anchor assembly illustrating the hex head removably attached to the upper end. 
     FIG. 4 shows an enlarged side elevational view of the hex head of the shaft shown in FIG.  3 . 
     FIG. 5 is an enlarged plan view of the hex head shown in FIG.  3 . 
     FIG. 6 shows a side elevational view of the hub of the anchor assembly, shown in FIG. 2, illustrating the helical assembly with the wings in the retracted position. 
     FIG. 7 shows a side elevational view of the hub of FIG. 2 illustrating the wings in the extended position. 
     FIG. 8 shows a plan view of the hub of FIG. 2 with the wings in the retracted position. 
     FIG. 9 shows a plan view of the hub of FIG. 2 with the wings in the extended position. 
     FIG. 10 shows a side perspective view of the hub of FIG. 2 illustrating the helical assembly with the wings in the retracted position. 
     FIG. 11 shows a side perspective view of the hub of FIG. 2 with the wings in the extended position. 
     FIG. 12 shows a perspective view of the skirted plate of the cap assembly. 
     FIG. 13 shows a longitudinal, partially sectional view of the anchor assembly of FIG. 2, showing the nut driving sleeve engaged with the nut to press the cap assembly further into the earth. 
     FIG. 14 is an exploded view of the attachment collars and associated bracket assembly by which the anchor assemblies are connected to the boring machine 
    
    
     BACKGROUND OF THE INVENTION 
     Horizontal boring machines are used in industry to tunnel boreholes underground usually for the installation of utilities. Typically, the boring machine is secured to the earth at the bore site by connecting the machine to anchors embedded in the earth. High thrust and torque pressures combined with varying soil conditions may loosen the grip of the anchors in the soil. Thus, there remains a continuing need to improve these “earth anchors” to provide increased resistance to dislodgement in response to forces of the drill string and the boring machine. This will reduce the instances where interruption of the boring operation is required to reset a loosened anchor. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides an improved anchor assembly that combines enhanced threaded engagement with a clamping assembly. The threaded engagement of the helical assembly with the earth is enhanced by expandable wings that engage undisturbed soil after the anchor is completely embedded. Then, a cap assembly at the surface clamps or compresses the soil between the embedded, expanded helical assembly and the front of the boring machine, which augments the gripping force of the expanded helical assembly. In addition, this arrangement enhances lateral stability of machine. The helical configuration facilitates insertion and removal of the anchor by rotation and counter-rotation. These and other advantages of the present invention will be apparent from the following description of the preferred embodiments. 
     Turning now to the drawings in general, and to FIG. 1 in particular, shown therein is a boring machine constructed in accordance with the present invention and designated generally by the reference numeral  10 . The boring machine  10  is adapted to advance a drill string  12  horizontally underground to form a borehole  14  for the purpose of installing utility lines and the like. The drill string  12  usually comprises a plurality of drill pipes joined end to end in sequential fashion while the machine  10  advances the string. Once the borehole  14  is completed, the drill string  12  is withdrawn and disassembled pipe by pipe. However, it will be understood that for the purposes of the present invention a drill string of continuous tubular material may be used. 
     The boring machine  10  generally comprises a frame  16  which supports a drive assembly  18  of any type suitable for advancing the drill string  12  to form the borehole  14  in the earth  20 . For example, commercially available boring machines utilize percussive force, continuous thrust and rotary boring type systems. These systems may be powered pneumatically, electrically, hydraulically, or otherwise, depending on the nature of the boring head and the terrain. In that regard, the terms “earth” and “soil,” as used herein, encompass any type of soil, such as sand, clay, rock, gravel, and combinations of these. 
     To stabilize the boring machine at the bore site, the frame  16  of the machine  10  is stabilized by at least one anchor assembly  22  connectable to the frame in a manner to be described. Preferably, the boring machine  10  comprises more than one anchor assembly  22  and more preferably the boring machine comprises four or more anchor assemblies positioned in front of and on both sides of the machine, all of the anchor assemblies being designated by the same reference numeral  22 . The number and position of the anchor assemblies  22  will be selected depending on the size of the machine, the drive force being exerted by the machine, the condition of the soil, the resistance between the borehole and the drill string, and other factors. 
     As all the anchor assemblies are similarly constructed, only one will be described in detail herein. Turning, then, to FIG. 2 the preferred construction of the anchor assembly  22  now will be explained. 
     The anchor assembly  22  generally comprises a shaft  24  having an upper portion  26  and a lower portion  28 . The lower portion  28  is adapted for piercing and screwing into the earth  20 , while the upper portion  26  is adapted to connect to the frame  16  of the boring machine  10  and to attach the anchor assembly to a powered rotary motor drive  30  (see FIG.  1 ), which may or may not comprise part of the boring machine. As the rotary drive is of conventional design, and several suitable types are commercially available, it will not be shown or described in detail. 
     With continuing reference to FIG. 2, the upper portion  26  of the shaft  24  may be integrally formed with the lower portion  28  or separately made and permanently affixed thereto. Alternatively, and preferably, the lower portion  28  of the shaft  24  may be a separate portion, referred to herein as a hub  32 , which is removably connectable to the upper portion  26 . This allows interchangeability of parts. In this way, if either the upper portion of the shaft or the hub becomes damaged the undamaged part may be reused. In addition, hubs having different sizes, lengths and helical assemblies (to be described) can be selected according to soil type, machine size, and so forth. 
     The hub  32  has an upper end  34  and a lower or downhole end  36 . The downhole end  36  of the hub  32  (or the lower portion of an integral shaft) preferably is provided with a bit  38 . The bit  38  may be a pointed or beveled end integrally formed on the hub  32  or a removable, replaceable bit. 
     The upper end  34  of the hub  32  is adapted to removably connect to the lower end  40  of the upper portion  26  of the shaft  24 . Referring now also to FIG. 3, the preferred configuration for the shaft  24  is illustrated. The lower end  40  of the shaft  24  is provided with a connecting portion  42  extending therefrom, and the upper end  34  of the hub  32  is shaped to receive the connecting portion  42 . In the embodiment shown, the upper end  34  of the hub  32  is tubular and the connecting portion  42  is a tubular member of reduced diameter. The telescopic connection formed thereby is secured in some manner as by a roll pin  44  (FIG. 2) receivable in the cross bore  46  in the connecting portion. It will be appreciated, however, that many different means can be used to connect the hub  32  to the lower portion  40  of the shaft  24 , such as friction fit, crimping, ring clamps, set screws and adapters of various configurations. 
     Referring still to FIG. 3, and also now to FIGS. 4 and 5, the upper end  50  of the shaft  24  is provided with an adapter for connecting the shaft to the rotating drive motor  30  (FIG.  1 ). The nature of the adapter, of course, will depend on the connection to the motor  30 . In the embodiment shown herein, the adapter takes the form of a hexagonal ball adapter  52 . The ball adapter  52  is connected to the upper end  50  of the shaft  24  by means of a stopper  54 , but any suitable connection may be substituted which will permit rotation from the motor  30  to be transmitted to the shaft  24 . 
     With continuing references to FIG. 3, the upper portion  26  of the shaft  24  is threaded for a reason that will become apparent. The threads  56  may be formed in the shaft by molding, machining or by attaching a separately formed helical member in a known manner. 
     Attention now is directed to FIGS. 6-9 for a more complete description of the hub  32 . The hub  32  is provided with a helical assembly  60  supported thereon. The helical assembly  60  comprises at least one helical flight attached to the hub  32 , as by welding or some other manner. Preferably, the helical assembly  60  comprises a plurality of flights, and even more preferably two flights  62  and  64 . Now it will be understood that the helical pattern of the flights  62  and  64  renders the shaft  24  insertable into the earth by screwing or rotating the shaft in a first direction and axially advancing the shaft. Likewise, the shaft  24  is thereby rendered removable from the earth by rotating the shaft in second direction opposite the first direction (“counter-rotating”) and axially withdrawing the shaft. 
     With continued reference to FIGS. 6-9, the helical assembly  60  further comprises at least one wing and preferably a plurality of wings. More preferably, the helical assembly  60  comprises two wings  66  and  68 , one carried by each of the flights  62  and  64 . 
     The wings  66  and  68  are supported adjacent the hub  32  and are movable between an extended position and a retracted position. More specifically, the wings are connected in a manner that urges the wings toward the retracted position as the shaft is inserted into the earth, and that urges the wings toward the extended position when the shaft is counter-rotated. FIG. 6 illustrates the retracted position of the wings  66  and  68  and the diameter of the helical assembly is indicated at D 1 . FIG. 7 illustrates the extended position of the wings  66  and  68  and the expanded diameter of the helical assembly is indicated at D 2 . 
     Now it will be appreciated that, as the hub  32  is screwed into the earth, the helical assembly  60  cuts a helical path through the earth of the dimension of D 1 . However, upon a partial counter-rotation, which forces the wings  66  and  68  into the extended position shown in FIGS. 7 and 9, the extended wings will be cutting a wider helical path into the earth digging into soil not previously disrupted when the shaft was being rotated for insertion. 
     While many configurations of the wings and flights will accomplish this effect and are within the scope of this invention, one preferred configuration is illustrated. The flight  62  comprises a pair of opposing, parallel upper and lower center plates  72  and  74  and a laterally extending planar side plate  76  partially sandwiched therebetween. The wing  66  is also planar and partially sandwiched between the center plates  72  and  74 . However, the wing  66  is pivotally attached by the pin  78 . The flight  64  comprises a side plate  82  and upper and lower center plates  84  and  86 . In this embodiment the side plates are rigidly fixed to the center plates, and the center plates are rigidly attached to the hub. 
     Now it will be apparent that as the hub  32  is rotated clockwise, as shown in FIGS. 6 and 8, the edge  90  of the side plate  82  and the edge  92  of the side plate  76  form the leading edges of the helical assembly  60 . As shown in FIGS. 7 and 9, as the hub  32  is rotated counter-clockwise, the edge  94  of the wing  66  and the edge  95  of the wing  68  are the leading edges. 
     Reference now is made also to FIGS. 10 and 11, which show a perspective view of the hub  32  and helical assembly  60  in the retracted and extended positions, respectively. FIGS. 6-11 further illustrate the operation of the helical assembly, as well as the three dimensional configuration of the flights and wings. The side plates  76  and  82  are positioned in the same planes as the wings  66  and  68 , respectively. The side plates  76  and  82  and the wings  66  and  68  are contoured to move between the top and bottom plates  72  and  74  and  84  and  86 , respectively, so that the wings can pivot around the pins  78  and  79 , respectively, in and out of the extended position. Pivotal movement of the wings  66  and  68  may be limited by forming the rear lobes  96  and  97  of the wings to abut the forward corners of the side plates  76  and  82  which serve as stops  98  and  99 . 
     When the hub  32  is rotating during insertion, as illustrated in FIGS. 6,  8  and  10 , the edges  90  and  92  of the side plates  76  and  82  are cutting into the soil and the wings  66  and  68  are following. In this direction, the wings  66  and  68  are maintained in the retracted position by the friction of the soil. 
     On the other hand, when the direction of rotation is reversed, as shown in FIGS. 7,  9  and  11 , the edges  94  and  95  begin cutting into soil, including soil undisturbed by the first pass in the opposite direction. The pressure of the soil against the edges  94  and  95  pushes the wings  66  and  68  out into the extended position. Thus, the wings  66  and  68  are expanded by a partial counter-rotation. 
     As illustrated in FIGS. 6-11, the wings  66  and  68  are helically aligned with the flights  62  and  64  in both the retracted position and in the extended position. As used herein “helically aligned” with reference to the wings denotes a helical pattern compatible with the helical pattern of the flights. Accordingly, the wings may be in the same plane as the flights or parallel thereto, so long as the wings do not interfere substantially with the screwing action imparted by the helical flights. 
     The leading edges  90  and  92  may be provided with flaps  100  and  102  angled downwardly to aid in directing the helical assembly during insertion. In a like manner, the edges  94  and  95  of the wings  66  and  68  may be provided with flaps  104  and  105  angled upwardly to aid in directing the helical assembly upward during withdrawal. 
     In some instances, such as where the anchor assembly  22  is being driven into hard or rocky soil, it will be desirable to lock the wings  66  and  68  into the retracted position. For this purpose, the helical assembly  60  may be provided with wing locks. With continued reference to FIGS. 8-11, the preferred wing lock may take the form of bolts  106  and  107  (FIG. 8) receivable in holes  108  and  109  (FIGS. 9-11) in the flights  62  and  64 , respectively, and aligned holes (not shown) in the wings  66  and  68 , respectively. By inserting the bolts  106  and  107 , the wings  66  and  68  are locked into the retracted position. When the bolts  106  and  107  are removed, the wings  66  and  68  function as described previously. 
     Now it will also be understood that a plurality of boltholes could be provided for locking the wings into different degrees of extension. In this way, the helical assembly could be provided with an adjustable diameter. 
     Turning once again to FIGS. 1 and 2, the anchor assembly  22  preferably comprises a cap assembly  110 . The cap assembly  110  comprises a plate  112  having an aperture  114  (see also FIG. 12) sized to receive the shaft  24 . The aperture  114  may be provided with a short neck  116 . While the plate  112  is shown as planar, it may be convex or concave, solid or not solid, and may have shapes other than round, such as square or hexagonal. 
     Depending from the plate  112  is an earth engagement member disposed to engage the surface of the earth  20  as the plate is pressed downwardly. Preferably, the earth engagement member takes the form of a cylindrical skirt  120  with a serrated edge  122  for facilitating the penetration of the edge  122  into the soil. The plate  112  preferably has a diameter greater than the diameter of the skirt  120  to provide a peripheral flange  124  that overhangs the skirt. The preferred plate/skirt configuration is better illustrated in FIG.  12 . It should be understood, however, that the earth engagement member can take many forms, such as a plurality of depending spikes or prongs, and it may take shapes other than cylindrical. For example, the engagement member could be square or hexagonal. Preferably, though, the plate  112  has generally the same shape as the engagement member. Finally, the serrated edge  122  can take several forms such as pointed, as shown in FIG. 2, or notched, as shown in FIGS. 12 and 13. 
     Regardless of its form, the relatively large vertical surface of the earth engagement member extends generally perpendicular to the longitudinal axis of the drill string  12  and the pushing and pulling forces on the boring machine  10  during a drilling job. Thus, this vertical surface area provides substantial resistance to the lateral displacement forces acting on the machine and significantly improves the stability of the anchors. 
     As explained previously, the upper portion  26  of the shaft  24  preferably is provided with threads  56 . Now the purpose of this feature will be explained. The cap assembly  110  comprises an anchor lock that is engageable with the upper portion  26  of the shaft  24  to appress the plate  112 . A lock nut  126 , threadedly receivable on the threads  56  of the shaft  24 , is ideal for this purpose. While the lock nut  126  is ideal, other devices may be substituted successfully, such as cam-operated tongs or slips, or vertically adjustable clamps. The preferred configuration for the lock nut is polygonal, and more preferably square, for a reason discussed hereafter. 
     A preferred device for threading and tightening the lock nut  126  is illustrated in FIG.  13 . The device is a drive connection sleeve  130  preferably comprising a tubular body  132  sized to receive the upper portion  26  of the shaft  24 . The lower end  134  of the sleeve  130  is formed into a wrench portion  136  non-rotatingly engageable with the square lock nut  126 . The upper end  138  of the sleeve  130  is provided with an adapter by which the sleeve can be connected to a rotary drive motor. Preferably, the adapter is a hexagonal ball  140  similar to the ball adapter  52  on the shaft  24 . In this way, the sleeve  130  can be driven by the same motor  30  (see FIG. 1) and connection system used for driving the rotation and counter-rotation of the shaft  24 . 
     Turning now to FIG. 14, and with continuing reference to FIGS. 1,  2  and  13 , an attachment frame may be used to connect the anchor assembly  22  to the frame  116  of the boring machine  10 . While the structure of the attachment frame may take many forms, in the preferred embodiment the attachment frame comprises a collar  144 . The collar  144  comprises a cylindrical neck  146  with a peripheral flange  148 . The flange  148  provides a broad base to support the collar  144  on the surface of the earth  20 . The diameter of the neck  146  preferably is selected to receive the skirt  120  of the cap assembly  110  therethrough. The height of the neck  146  selected to engage the flange  124  of the plate  112  when the lower portion of the skirt  120  is embedded in the soil  20  around the shaft  24 . 
     An extension  150  extends from the collar  144 , and preferably from the flange  148 , to connect to the frame  16  of the machine  10  in any suitable manner. As explained herein, in most instances two to four anchor assemblies will be used for a single machine. For this reason it is advantageous to provide the machine with a bracket assembly  152  which allows multiple attachment collars to be attached in a selected arrangement, as illustrated in FIG.  14 . 
     In some instances, it may be advantageous to consolidate the functions of the above described cap assembly  110  and the collar  144  by integrating these structures. This may be carried out by providing a cover plate on the top of the neck  146  and a depending skirt extending from the bottom of the flange  148 . 
     Having described the structure of the present invention, the operation will now be explained. As illustrated in FIG. 1, the boring machine  10  is first positioned at a selected site. Next, the number and position of anchor assemblies are determined. Then, the anchor assemblies are installed. 
     Installation of the anchor assembly begins with the placement of the attachment collar  144 . Next, the bit  38  on the hub  32  of the shaft  24  is pointed at the desired insertion point inside the collar  144 . Then, the cap assembly  110  is positioned by inserting the shaft  24  through the aperture  114  of the plate  112  and then nesting the skirt  120  inside the neck  146  of the collar  144 . The shaft is rotated by connecting the motor  30  to the hex ball  52 . The helical assembly  60  screws the shaft into the ground. Once the shaft  24  is embedded to the desired level, the direction of the motor  30  is reversed and the shaft  24  is counter-rotated about one-quarter revolution. This reverse rotation spreads the wings into the extended position, better engaging the helical assembly in the soil. 
     Having implanted the shaft  24  in the earth, the connection to the motor  30  is removed. The skirt  120  is pressed down into the ground and embedded therein. Next, the hex nut  126  is manually threaded down the upper portion  26  of the shaft  24  until the nut engages the neck  116  of the plate  112 . 
     To tighten the nut  126  against the cap assembly  110 , and the plate  112  against the collar  144 , the connection sleeve  130  (FIG. 13) is placed over the shaft  24  and positioned so that the wrench portion  136  engages the nut  126 . Then, the motor  30  is connected to the hex ball  140  on the upper end  138  of the sleeve  130 , and the nut is driven until the plate  112  contacts the top edge of the neck  146  of the collar  144 . This inserts the skirt  120  into the earth  20  to provide maximum resistance to lateral movement of the machine  10  on the surface of the earth  20 . Further, this compresses the soil  20  between the helical assembly  60  and the cap assembly  110 , clamping the soil as illustrated by the bi-directional arrow “C” in FIG.  13 . 
     When the boring operation is completed, the anchor installation process is performed in reverse. Now it will be appreciated that, while the expanded wings embedded in the undisturbed soil resist dislodgement of the anchor during operation of the boring machine, the helical alignment of the wings facilitates the removal of the anchor by counter-rotation. 
     The anchor assembly of this invention has been described as particularly applicable for use with a horizontal boring machine to stabilize the machine at the bore site. It will be appreciated, however, that the present invention has many other applications and could be utilized to secure any object to any compressible material into which the anchor can be driven. It will therefore be apparent that, as used herein, “compressible material” means any material that is amenable to insertion of a helical member. 
     Changes may be made in the combination and arrangement of the various parts, elements, steps and procedures described herein without departing from the spirit and scope of the invention as defined in the following claims.