Abstract:
A hole opener and method for using same which allows for a greater number of cone utters to be attached to the hole opener. The support structure provided by the present invention uses a barrel which is attached to the drill stem to effectively increase the diameter of the drill stem so that additional cutters may be attached to the hole opener. Using the barrel structure, the structural integrity of the tool is not compromised, and a strong support structure for the cutters is provided. The cone cutters may be removable from the barrel. The removable structure is provided by placing a bolt inside the segments which is used to mate the segment with a pocket attached to the barrel. This results in a very versatile tool in that the same boring head may be used for boring various types of materials. The barrel structure of the present invention also provides a means for trapping cones inside the barrel to prevent the cone cutters from being left inside the hole. The tapered shape of the hole opener allows it to be forced back to the point of entry after drilling in order to displace debris.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a hole opener boring apparatus and method for using such and more particularly to an improved mounting structure for a hole opener that allows a greater number of cutters to be placed on the hole opener. 
     2. Description of Related Art 
     Hole openers are used when pipelines, cables, or culverts, for example, must be installed under surface barriers such as highways, buildings, waterways and other surface obstructions without disturbing the surface. Before a hole opener is used, a trench is opened on both sides of the barrier. A pilot bore is formed under the barrier. If the pilot bore is of insufficient diameter to install the pipeline, then the hole may be opened up using a hole opener. Next a boring head which is also referred to in the art as a reamer or hole opener, is used to enlarge the pilot bore. Generally, a guide is positioned on the advancing side of the boring head. The guide on the boring head is designed to engage the walls of the pilot bore and help steer the pipeline boring head while the pilot bore is being enlarged. Drilling fluids are also supplied to the boring operation through the drill stem in the pilot bore to produce a slurry which floats the drilled material out the end of the hole. After a hole is opened up using the hole opener, a section of the pipeline is either pushed or pulled lengthwise through the bore from one side of the barrier to the other. The pipeline may also be pulled through by the hole opener as the hole is being opened. The installed pipeline section may then be welded into place and tested. 
     Various types of reamers or hole openers have been disclosed in the prior art. One such opener has cone cutters which are mounted around the circumference of an axial shaft called a drill stem that is used to drive the hole opener. These cutters have been mounted by attaching plates perpendicular to the drill stem to which the cutters are then attached. The number of cutters that may be mounted to the drill stem using current methods is limited because of the tremendous forces placed on the cone cutters when in operation. The support structure attached to the drill stem must be sufficiently strong to prevent excessive breakage during a drilling operation. 
     Because of the limitations posed by the current support structures used to mount the cutters to the drill stem, the number of cone cutters that may be placed around the circumference of the boring head is limited. This limitation in the number of cutters varies depending on the diameter of the cutter. However, regardless of the diameter of the cutter, the structural methods used in the prior art severely limit the number of cutters allowed. Thus, the prior art tools are very rough in operation when used in hard material such as rock or hard gravel. The prior art tools also require much more power than would be required if more cutters could be added to the circumference of the tool. The prior art hole openers are analogous to a square wheel in that they are very rough in operation, and they tend to produce holes which are elongated or egg-shaped because of the rough operation. The rough operation also increases the likelihood that the cone cutters will break and be left in the hole. The removal of cone cutters from a prior art boring head after a drilling operation has proven to be very difficult and expensive because of the primitive attachment means that have been used. 
     Furthermore, the tools of the prior art could not be pushed backwards through the hole easily because the tools had a tendency to sink or grab along the edges of the holes due to the flat backs of the tools. The use of only four cones on prior art devices causes excessive friction between the tool and the walls of the hole making it even more difficult to push the tools back through the hole. Thus, it is virtually impossible to push prior art tools back through the hole in order to smooth the jagged edges inside the hole and mechanically push debris out of the hole. In order to produce a clean hole using prior art tools, the tool is pulled through very slowly while drilling fluids are liberally applied at the hole opener to produce a slurry that floats the debris out of the hole. Alternatively, a different tool may be attached to the drilling rig for pushing the debris out of the hole. However, this is very time consuming because of the time required in changing the tools and is more expensive because a separate tool is required. 
     Therefore, it would be desirable to provide a hole opener more analogous to a round wheel to reduce vibration and to reduce the size of the power supply required to operate the tool. A reduction in the size of the power supply would allow smaller boring machines to enter markets which were previously open only to larger drilling rigs. A support structure for the hole cutters is needed which will accommodate an increased number of cone cutters around the circumference of the boring head to provide a hole opener which operates smoothly. It is also desirable for the hole cutter to be capable of collecting cone cutters as they break off to avoid leaving the broken cone cutters in the hole and thereby reduce the expense of drilling operations. Furthermore, the cone cutters should be easily removable so that new or different styles or sizes of cone cutters may be installed between drilling operations. Finally, the hole cutter should be capable of being pushed back through the hole in order to provide an effective and efficient means for mechanically pushing the material out the end of the hole without requiring the insertion of a different tool. 
     SUMMARY OF THE INVENTION 
     The present invention provides a hole opener support structure which allows for a greater number of cone cutters to be attached to the hole opener. Increasing the number of cone cutters decreases the roughness of operation of the hole opener and produces a hole which is round rather than oblong or egg-shaped. Consequently, much less power is required to operate a hole opener of the same diameter than is required by the prior art tools. The support structure provided by the present invention uses a barrel which is attached to the drill stem to effectively increase the diameter of the drill stem so that additional cutters may be attached to the hole opener. Using the barrel structure, the structural integrity of the tool is not compromised, and a strong support structure for the cutters is provided. The tapered shape of the hole opener allows the hole opener to be easily pushed back through the hole to displace debris left behind the hole opener as the hole is being cut. Because debris may be mechanically displaced from the hole using the method of the present invention, much less drilling fluid is required to open a hole. 
     In one embodiment of the present invention, the barrel has openings in the front and back to allow drilling fluid and material to pass through the hole opener. The openings are such that broken cone cutters are deposited through the front openings and trapped in the barrel, thereby preventing the broken cone cutters from being left in the hole. Furthermore, the cone cutters may be easily removed from the barrel between drilling operations. This feature is provided by embedding a bolt in a groove within the cone cutter segment. The bolt is used to secure the segment to a pocket attached to the barrel. Because the bolt itself is replaceable, the life of the cone cutter segments are prolonged. This results in a very versatile tool in that the same hole opener may be used for boring various types of materials, and less time is required to change worn-out cone cutters. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a front perspective view of an embodiment of a hole opener in accordance with the present invention. 
     FIG. 2 is a side view of the hole opener of FIG. 1 with segments removed. 
     FIG. 3 is a side view of the hole opener of FIG. 1 as illustrated with segments installed into tapered pockets. 
     FIG. 4 is a rear perspective view of the hole opener of FIG.  1 . 
     FIG. 5 is a front perspective view illustrating another embodiment of a hole opener in accordance with the present invention. 
     FIG. 6 is a top view of a segment used in one embodiment of the present invention. 
     FIG. 7 is a side view of a segment used in one embodiment of the present invention. 
     FIG. 8 is a bottom view of a segment used in one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, a front perspective view of an embodiment of a hole opener in accordance with the present invention is illustrated. A drill stem  105  extends from the front of the cutter to act as a pilot and a drive shaft for the hole opener. The drill stem  105  is threaded to allow extensions of the drill stem  105  to be attached. The drill stem  105  passes through a pilot hole that is bored prior to the insertion of the hole opener. The drill stem  105  is hollow for pumping drilling fluid through the drill stem and out fluid ports to liquify the material into a mud so that it more easily passes through or around the hole opener during the drilling operation. Water tubes  110  in fluid communication with the drill stem  105  may be attached to the drill stem to act as a fluid communicator to spray water out over the loose material. The water tubes  110  have several small holes drilled in them to allow the water to be dispersed at different intervals along the hole opener. Attached to the drill stem  105  is a front plate  115  and a rear plate  120  that extend substantially perpendicular from the drill stem  105 . Bridging the outer edges of the front plate  115  and the rear plate  120  is a cylindrical ring  125 . The ring need not be cylindrical but could, for example, be in the shape of a polygon with a number of sides depending on the number of cutters to be installed on the hole opener. The cylindrical ring  125  can be a steel pipe of the appropriate diameter that is welded to the outside edges of the front and rear plates  115 ,  120 . The diameter of the plates  115 ,  120  and cylindrical ring  125  is dependent upon the desired diameter of the cutting tool. The combination of the front plate  115 , the rear plate  120 , and the cylindrical ring  125  is referred to herein as a barrel because a hollow cylindrical structure is formed around the drill stem  105 . In alternate embodiments, the barrel need not be formed of separate pieces but could be cast as one individual piece having holes through which the drill stem may be inserted and secured in place. 
     For tools of sufficient diameter, material ports  130  may be located in both the front plate  115  and the rear plate  120 . The material ports  130  allow material such as dirt, mud, and rocks to pass through the hole opener while it is in operation. Material ports such as these can be placed in the front plate  115  and rear plate  120  without compromising the structural integrity of the support structure for the cone cutters  135 . For a hole opener of sufficient diameter, the material ports in the front plate  115  can be made large enough such that if a cone cutter  135  breaks off during operation it will pass through one of the material ports  130  in the front plate  115  and be trapped inside the barrel. The material ports in the back plate are made smaller than the cone cutter  135  so that the cone cutter  135  cannot pass through the material ports in the rear plate  120 . Thus, whenever the hole opener is pulled from the hole the cone cutter  135  that was broken off is also removed. Normally, if a cone cutter is left in the hole, the hole must be redrilled at a different location. Thus, considerable expense is saved by producing a hole which is clean and free of debris or other material that would damage a pipe as it is being pulled into the hole. Although the embodiment of FIG. 1 shows four material ports of a rectangular shape, any number of ports of various shapes may be used without departing from the scope and spirit of the invention. Furthermore, although an equal number of material ports are shown in the front plate  115  and the rear plate  120 , a different number of ports could be placed in the rear plate  120 . As an example, if the material ports in the rear plate are smaller than those in the front plate  115  it may be desirable to provide a greater number of ports in the rear plate  120  to allow the material to flow through more easily. Thus, it is also obvious that the material ports in the front plate need not be in alignment with the material ports in the rear plate. 
     Each cone cutter  135  is attached to a support arm which is described in greater detail below. The support arm of each cone cutter  135  is attached to the cylindrical ring  125 . The cone cutters  135  can have different patterns for the rows of teeth to avoid a strip in the hole being drilled which is not being touched by the teeth. Two different cutter patterns  135   a ,  135   b  are shown in FIG.  1 . The invention is not limited to a hole opener with only two cutter patterns. The tool could have four or more different patterns depending on the number of cone cutters to reduce vibration. For example, the use of a four-cone pattern further reduces vibration by requiring each cone to cut less material than would a three-cone pattern. The present invention, by allowing more cutters to be placed around the circumference of the hole opener, also allows a greater number of cone patterns to be implemented. 
     The combination of the cone cutter with the support structure is referred to herein as a segment  140 . Tapered pockets  145  are attached around the circumference of the barrel to provide a receptacle for the segments  140 . Thus, the segments  140  may be removed and replaced as they wear out or as different types of material are encountered requiring different types of cone cutters. It is well known in the art that the cone cutters  135  will vary depending upon the type of material that is being bored. Cone cutters of different type and orientation than that shown in FIG. 1 may be used without departing from the scope and spirit of the invention. Furthermore, a combination of different types of cutters may be used at the same time to provide a more efficient hole opener. In addition, cone cutters of a different diameter than those shown in FIG. 1 could be used to change the overall diameter of the hole opener, thereby making small changes in the diameter of the resulting hole as desired. 
     Typically, the hole opener is pulled through the pilot hole using the drill stem  105 . A power source is attached to the front side of drill stem  105  to provide a rotational force as well as a pulling force for operating the hole opener. If the hole opener is operated in a counter-clockwise direction  150 , each of the cone cutters rotate in a direction  155  opposite the rotation of the tool as they contact the material being drilled. 
     Referring now to FIG. 2, a side view of the hole opener of FIG. 1 is illustrated with the segments  140  removed. Throughout the detailed description, like numerals are used to denote like parts unless otherwise noted. The tapered pockets  145  are preferably made of mild steel and welded to the barrel  125 . Mild steel allows a certain amount of stretch which results in a tighter fit for the segments  140 . The water tubes  110  are placed adjacent to the front plate  115  behind the cutting plane of the cone cutters  135 . 
     Referring now to FIG. 3, a side view of the hole opener of FIG. 1 is illustrated with the segments  140  installed into the tapered pockets  145 . The removable segments  140  may be secured using a locking hexnut  305  or may be double nutted to prevent inadvertent loosening of the segment during operation. Tightening the hexnut produces a friction lock between the segment  140  and the tapered pocket  145 . A flange  310  protruding from segments  140  is used to provide a stop to indicate that segment  140  has been drawn completely into the tapered pocket  145 . 
     Referring now to FIG. 4, a rear perspective view of the hole opener of FIG. 1 is illustrated. The material ports  405  in the rear plate  120  are smaller than the material ports  130  that are in the front plate. This prevents a broken cone cutter  135  from passing through the barrel  125  once it is trapped inside. The rear end of the drill stem  105  may be threaded to allow the attachment of additional hole openers of larger diameter depending on the diameter of the hole that must be drilled and the power source available to drive the tool. Thus, if sufficient power is available, a large diameter hole may be opened using two or more hole openers of increasing diameter attached in series. If an additional hole opener is not being used, then the rear end of the drill stem may be capped to prevent water from flowing out of the drill stem and to protect the threads on the drill stem. 
     Referring now to FIG. 5, another embodiment of a hole opener in accordance with the present invention is illustrated. This embodiment has fewer cone cutters  135  than are illustrated in the embodiment of FIG. 1 to allow the diameter of the hole opener to be decreased while keeping the same size cone cutters. In this embodiment there are no holes in the front plate  510  or the rear plate (not shown). This is because there is not enough room between the drill stem  520  and the cone cutters  135  to allow for material ports. However, for a cutter of this size, there is sufficient room between the cone cutters  135  for material to pass. Because the diameter of the hole is much smaller, there is less material that is required to be passed by the cutter, and therefore, the holes in the plates are unnecessary in this embodiment. The tapered design of the hole opener from front to back, as can be seen in FIG. 2 or FIG. 3, also allows for the passage of material over the top of the segments  140 . 
     The tapered design of the embodiment of the invention shown allows the hole opener to be easily pushed back through the hole that has been cut. The hole opener may also be rotated as it is being pushed back through the hole. This “double cutting” of the hole provides a much cleaner hole than was possible with prior art tools by pushing the loose material out of the hole. When drilling a hole of a length that requires the use of multiple segments of drill stem, the hole opener may be pushed back to the point of entry before removing each segment of the drill stem. This process makes it easier to mechanically push debris out of the hole because the debris is removed in smaller portions. Then, when the hole is drilled all the way through, the tool can be pushed back to the point of entry one final time and attached to the pipeline or cable and pulled back through the hole for removal at the point of exit. Using this method, it is not necessary to flood the hole with enough drilling fluid to wash the debris out of the hole. Thus, much less drilling fluid is used and a cleaner hole results. 
     The barrel  505  may be made from a pipe of smaller diameter than that in FIG. 1, but it accomplishes the same purpose of providing a support structure for the cone cutters  135  which allows more cone cutters  135  to be placed around the diameter of the hole cutter than was allowed using prior art methods. Therefore the tool is much smoother operating and requires less power to operate. This embodiment also illustrates the use of a water reservoir  525  rather than the water tubes  110  shown in FIG.  1 . The reservoir can be made using a reducer by welding it to the front plate  510  and the drill stem  520 . Holes are cut in the reservoir  525  to allow water to be dispersed and mixed with the loose material. Water is pumped into the reservoir  525  through holes drilled in the drill stem  520  located inside the reservoir  525 . 
     Referring now to FIG. 6, a top view of the segment  140  shown in FIG.  1  and FIG. 5 is illustrated. The flange  310  used to provide a stop for the segment  140  is illustrated in greater detail. The taper  605  of the segment is also illustrated. This tapered design allows a wedge fit between the segments  140  and the pocket  145  thereby securing the segment  140  tightly to the barrel  125  to avoid movement caused by excessive forces during operation. 
     Referring now to FIG. 7, a side view of the segment  140  is illustrated. The tapered support arm  705  of the segment  140  is tapered along several planes to prevent the segment from twisting or turning inside the pocket during operation. The bottom  710  of the tapered arm may be curved slightly to allow a snug fit with the barrel. Thus the bottom is relatively flat compared to the remainder of the tapered arm  705 . Alternatively, the support arm could be cone-shaped with a keyway cut in the support arm for inserting a key which would mate with a keyway inside a cone-shaped pocket. Thus the tapered arm could be cone shaped without the planes used in the embodiment shown. Other emodiments of this pocket structure may be used without departing from the scope and spirit of the invention. 
     Referring now to FIG. 8, a bottom view of the segment  140  is illustrated. A slot  805  in the segment is provided for a hexhead bolt to be placed for meshing the segment  140  in the tapered pocket. The bolt slides down inside the slot  805  and is held in place by the barrel  125  as the segment is slid into the tapered pocket. The slot is such that the bolt is not allowed to rotate within the segment  140  when the segment  140  is placed inside the tapered pocket  145 . Because the bolt is removable from the slot whenever the segment is removed from the tapered pocket, the bolt may be replaced if it is damaged during removal or operation of the hole cutting tool. In fact, the bolt itself may be used to drive the segment out of the tapered pocket by removing the nut from the end of the bolt and hammering directly on the bolt. Obviously, when the bolt is hammered in this manner, the threads may be damaged, but because the bolt can be removed easily, it can be replaced with a new bolt when the segment is reinserted into the tapered pocket. If the segments were tapped with threads instead of using a bolt insert as described above, the whole segment would have to be replaced if the threads inside the segment were damaged or stripped. Thus, the present invention saves significant expense by increasing the life of the segments using the replaceable bolts. 
     Thus, the present invention provides a means for mounting segments on a hole opener which allows the segment to be spaced closer together while providing better structural support than is allowed in the prior art. The means for mounting the segments in the prior art limits the number of segments that may be placed in a plane perpendicular to the drill stem to four segments. Smaller boring heads may receive from one to two extra segments using the method of the present invention. The addition of extra segments increases the cutting surface of the tool and results in a smoother operation requiring less torque from the power source drill stem. The tool of the present invention also allows a finished hole which is more round than is allowed by the tools of the prior art. 
     While the invention has been particularly shown and described above with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For example, various types of cutters may be used. The tapered pockets for the segments could be of a different shape. Numerous types of attachments to the barrel itself may be used, and different styles of drilling fluid transfer could be used, all without departing from the scope and spirit of the invention.