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BACKGROUND OF THE INVENTION 
   1. Technical Field 
   This invention generally relates to boring equipment. More particularly, the invention relates to a cutting head for use in conjunction with boring machines to bore through a body of soil and simultaneously lay an underground pipe. Specifically, the invention relates to a rock head that is collapsed to reduce its diameter so that it can enter and travel through the bore of a pipe and that automatically expands to the original diameter once it exits the pipe. 
   2. Background Information 
   When underground pipes are to be laid, it is necessary to dig a hole through the soil to lay the pipe. This presents little problem if the pipe is to be positioned close the surface and there are no structures in the way. Then all that needs to be done is to dig a trench, put the pipe in place and fill the trench with soil. However, as urban development progresses, there is a growing need to be able to lay pipe quickly and efficiently and without causing damage to surface structures such as roadways. This can be accomplished by using a process known as auger boring. In this procedure, a boring machine is used to form a horizontal hole or passageway through the soil at the appropriate depth. If the terrain to be bored is hilly, the boring machine may be positioned proximate a hillside. If the terrain is flat, then an excavation pit is dug into the terrain to position the boring machine at an appropriate depth beneath the surface. In either instance, the boring machine is mounted on tracks so that it is able to slide toward and away from the surface into which the hole is being bored. Once the boring machine is in position, a flighted-auger is operationally connected to the boring machine and an appropriate cutting head is attached to the auger. The cutting head is placed into contact with the soil-face and the auger and cutting head are rotated by the boring machine so that the cutting head bores into the soil-face. As the cutting head cuts through the soil, the auger flights direct the excavated material away from the cutting head, out of the hole and to a location proximate the boring machine. Appropriate means are used to move the excavated soil out of the vicinity of the boring machine. Additional sections of auger are added as needed by sliding the boring machine away from the hole, positioning a new auger section rearwardly of the first auger section using a crane, and then securing the auger sections together. The boring machine is advanced forwardly along the tracks toward the soil-face until the next auger section is needed, and then another auger section is attached thereto. This procedure is repeated until the desired length of hole is cut through the soil. 
   In order to lay the pipe at the same time as the hole or passageway is excavated. In this instance, each section of auger is inserted into a length of pipe before it is lowered into place in front of the boring machine. The cutting head is then attached to the lead auger section. The cutting head needs to have a diameter that is slightly larger than the outside diameter of the pipe being laid, so that the bored hole is large enough to receive the pipe therethrough. The boring machine then advances both the pipe and auger as the cutting head cuts through the soil. The machine pushes the pipe through the soil, but rotates the auger within the pipe. Subsequent sections of auger and pipe are connected as needed. The sections of auger are connected together using the male and female hex connectors they are provided with. The sections of pipe are secured together by welding. 
   The cutting head selected for boring operations is dependent upon the type of substrate that is being drilled through. If the substrate is generally soil with small stones interspersed therethrough, then the type of cutting head used is known as a dirt head. Dirt heads cut easily and efficiently through soil. Sometimes, however, during boring operations, the dirt head will strike a large rock or a layer of rock. Dirt heads are ill equipped to cut through rock. In the past, if such an obstacle was encountered, then the first thing that was done was that a hole was dug down from the surface in an attempt to intercept and remove the rock, if possible. If, on the other hand, the rock was found to be too large, then the operators would use the dug hole to gain access to the dirt head, remove it from the front of the auger and replace it with a rock head. Rock heads are specially designed to cut through rock, but are fair less efficient at cutting through soil. Consequently, when the harder obstacle had been bored through, the operators would again have to dig down from the surface and replace the rock head with the dirt head. 
   If the hole was at too great a depth, then an alternative method of swapping the dirt head and rock head would be for the operators to withdraw the auger, pipe and dirt head from within the bored hole, cut the welds in the pipe as needed and disconnect the auger flights from each other. Then when everything was removed from the hole, the rock head would be attached to the lead auger, the auger would be repositioned in the hole and the boring machine would advance the auger and rock head through the hole until the rock or boulder was reached. The rock head would then be used to drill through the rock, then the auger and rock head would be withdrawn from the hole, the rock head removed, the lead auger repositioned within a pipe section and then the dirt head would be reattached to the lead auger. The dirt head and lead auger would then reinserted into the hole and boring would resume. All of this procedure took a considerable amount of time and effort depending on the length of hole and pipe involved. The time period for this type of exchange could extend to days. Alternatively, if the pipe was large enough, then the operator would simply withdraw the auger and dirt head and send a man with a hammer and chisel down the pipe to chip away at the rock involved. All of these methods of removing or boring through the rock would cost a lot of time, money, and effort and would slow the progress of the boring operation to a considerable extent. 
   There is therefore a need in the art for a rock head that can be quickly and easily attached to the front of an auger during boring operations that occur some depth from the surface without requiring tunneling down from the surface or removal of already installed sections of pipe and auger. 
   SUMMARY OF THE INVENTION 
   The device of the present invention is a rock head A rock head for use with an auger borer to bore a passageway through a body of soil and rock and simultaneously laying a pipe in that bored passageway. The rock head has a base connectable to the leading end of the auger. A plurality of movable mounts are provided on the base and a roller cone is secured to each movable mount. A spring is disposed between the movable mount and the base. The spring is compressed as the movable mount pivots the roller cones inwardly toward a central region of the base. This reduces the diameter of the rock head so that it can travel through the inside of the pipe. Each movable mount is provided with at least one wheel so that it can ride smoothly through the pipe. When the rock head exits the pipe, the springs automatically pivots each roller cone outwardly so that at least a portion thereof is disposed beyond the outermost edge of the base. In this second position, the rock head has a greater diameter than the pipe bore and therefore it cannot travel therethrough. When the auger is withdrawn through the pipe, the movable mounts pivot the roller cones from the second position back to the first position, thereby causing the rock head to collapse to a diameter sufficiently small enough to travel back through the pipe. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiments of the invention, illustrative of the best mode in which applicant has contemplated applying the principles, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims. 
       FIG. 1  is a front elevational view showing a boring machine equipped with a dirt head encountering a rock; 
       FIG. 2  is a front elevational view showing the boring machine with the auger extracted out of the pipe and with the dirt head removed; 
       FIG. 3  is a front elevational view of the front end of the lead auger and of a rock head in accordance with the present invention being positioned for attachment thereto; 
       FIG. 3A  is a perspective view of the base onto which the movable roller cones are mounted; 
       FIG. 4  is a front elevational view of the front end of the lead auger with the attached rock head being brought into the proximity of the back end of the pipe and showing the external diameter of the rock head exceeding the internal diameter of the pipe; 
       FIG. 4A  is an enlarged cross-sectional view of the upper pivoting roller cone of the rock head with the side wall thereof removed to show the spring; 
       FIG. 5  is an end view of the rock head in the second position; 
       FIG. 6  is a front elevational view of the front end of the lead auger and rock head showing the roller cones pivoting inwardly as the rock head enters the bore of the pipe; 
       FIG. 6A  is an enlarged cross-sectional view of the upper pivoting roller cones riding on the wheels through the bore of the pipe; 
       FIG. 7  is an end view of the rock head in the first position and contained within the bore of the pipe; 
       FIG. 8  is a front elevational view showing the boring machine moving the rock head and auger through the pipe toward engagement with the rock; 
       FIG. 9  is a partial cross-sectional front view of the front end of the pipe with the rock head about to emerge therefrom; 
       FIG. 10  is a partial cross-sectional front view of the front end of the pipe with the rock head extending out of the pipe, in the second position and in contact with the rock; 
       FIG. 11  is a partial cross-sectional front view of the front end of the pipe showing the rock head being withdrawn back into the pipe; and 
       FIG. 12  is a partial cross-sectional front view of the front end of the pipe with the rolling roller cones camming against the front end of the pipe. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , there is shown a boring machine  10  mounted on tracks  12  within an excavation pit  14 . Pit  14  extends for a depth below the surface  16  and exposes a soil-face  18  into which a hole  20  is being bored. The boring is accomplished by a dirt head  26  that is attached to a front end  22   a  of a flighted-auger  22 . Auger  22  is operationally connected to boring machine  10  and extends through the bore  32  of a casing or pipe  24 . Boring machine  10  advances both the auger  22  and pipe  24  through the soil  28 .  FIG. 1  illustrates that a large-bodied rock  30  lies in the path of the dirt head  26 . Inasmuch as the dirt head  26  is not suitable for boring through hard substances such as rock, dirt head  26  has to be replaced with a rock head (not shown in this Figure). 
   In order to replace dirt head  26  with a cutting head suitable for cutting through the rock  30 , the auger  22  and dirt head  26  have to be withdrawn from within bore  32  of pipe  24 .  FIG. 2  illustrates how boring machine  10  is slidably moved rearwardly on tracks  12  toward the back side of excavation pit  14  and remote from soil-face  18 . As boring machine  10  moves rearwardly, it draws auger  22  and dirt head  26  rearwardly and out of bore  32  of pipe  24 . The figure also illustrates that pipe  24  comprises a plurality of sections, such as first and second sections  36 ,  38  that are connected by a weld  34 . Once auger  22  is fully withdrawn from pipe  24 , then dirt head  26  is detached from the front end  22   a  of auger  22 . All of the steps described thus far are known in the prior art and are commonly practiced. 
   In accordance with a specific feature of the present invention, there is provided a collapsible rock head  40  for attachment to front end  22   a  of auger  22 . Rock head  40  is shown in detail in  FIGS. 3-7 . Rock head  40  comprises a substantially planar base  42  having a front surface  42   a  and a rear surface  42   b . A male hex connector  48  extends outwardly away from rear surface  42   b  of base  42 . Hex connector  48  is complementary sized and shaped to be received within a female hex connector  50  that extends outwardly from the front end  22   a  of auger  22 . As may be most easily seen from  FIG. 3A , base  42  includes a central region  52  that preferably has six wings  54  radiating outwardly away therefrom. The V-shaped gaps that are formed between adjacent wings  54  are provided so as to allow material excavated by the rock head  40  to be fed rearwardly onto the flights  22   b  ( FIG. 3 ) of auger  22 . 
   A plurality of drill bits are mounted on front surface  42   a  of base. The first group of drill bits is a tri-cone group  56  of roller cones that is fixedly mounted on central region  52 . The second group of drill bits  58  are each fixedly mounted on alternate wings  54  of base  42 . The third group comprises a plurality of drill bits  60  which are movably-mounted on wings  54  that alternate with those upon which drill bits  58  are mounted. 
   Referring to  FIG. 3 , each of the drill bits  56 ,  58 ,  60  is comprised of two components, namely a body and a roller cone rotatably mounted upon the body. So, the drill bits in the tri-cone group  56  each have a body  56   a  and a roller cone  56   b  mounted thereupon. The roller cone includes a plurality of cutting and grinding surfaces  62  which are made of any material sufficiently hard enough to fragment and crush rock, such as steel or tungsten. The exact structure of tri-cone group  56  is well known in the art. The bodies  56   a  of the drill bits in the tri-cone group  56  are fixedly mounted to base  42 . 
   Drill bits  58  have a body (not shown) and a roller cone  58   b  ( FIG. 5 ) rotatably mounted thereupon. The bodies of drill bits  58  are fixedly mounted to alternate wings  54  of base  42 . As is the case with drill bits  56 , the roller cones  58   b  include a plurality of cutting and grinding surfaces  62  thereon. 
   Drill bits  60  each comprise a body  60   a  and a roller cone  60   b  rotatably mounted thereon. Each roller cone  60   b  includes a plurality of cutting and grinding surfaces  62 . Unlike drill bits  56  and  58 , the bodies  60   a  of drill bits  60  are mounted to be movable between a first position (shown in  FIGS. 6A &amp; 7 ) where the roller cone  60   a  is positioned inwardly of the outermost edge  42   c  of base  42 ; and a second position (shown in  FIGS. 4A &amp; 5 ) where the roller cone  60   b  is positioned at least partially outwardly beyond the outermost edge  42   c  of base  42 . Body  60   a  includes an upwardly extending leg  64 , a front wall  66 , and a pair of spaced-apart side walls  68  which straddle leg  64  and front wall  66 . Leg  64  and walls  66 ,  68  are connected together in any suitable manner so that they move as a unit. Each body  60   a  is secured to a mounting bracket  74  ( FIG. 3A ) disposed on one of the alternate wings  54  on base  42 . Mounting brackets  74  are welded or otherwise attached to front surface  42   a  of base  42 . Each mounting bracket  74  includes an inner wall  76  and a pair of side walls  78 . The spacing between the exterior surfaces of side walls  78  preferably is substantially equal to the spacing between the interior surfaces of side walls  68 . Side walls  68  are each provided with an aperture (not shown) and side walls  78  are each provided with provided with a hole  79  therethrough. When body  60   a  is to be connected to mounting brackets  74 , the side walls  68  of body  60   a  are positioned outwardly of side walls  78  and the apertures and holes  79  are brought into alignment with one another. The apertures and holes  79  are sized to receive a retaining pin  80  therethrough. Each retaining pin  80  is inserted through a first aligned aperture and hole  79 , through a spring  82 , and then through the other aligned aperture and hole  79 . A snap ring  84  is then inserted into a groove (not shown) formed proximate each end of each pin  80 . Snap rings  84  prevent retaining pins  80  from being withdrawn from the aligned apertures and holes  79 . Retaining pin  80  locks body  60   a  to mounting bracket  74  in such a way that body  60   a  is able to pivot about retaining pin  80 , thereby making drill bit  60  movable relative to base  42 . 
   As may be most easily seen in  FIGS. 4A and 6A , drill bits  60  are spring-biased, each being mounted with a spring  82  has a first end  82   a  that abuts front wall  66  of drill bit  60  and a second end  82   b  that abuts inner wall  76  of mounting bracket  74 . Spring  82  is so positioned that as body  60   a  of drill bit  60  pivots about retaining pin  80 , the first end  82   a  of spring is forced inwardly toward the second end  82   b  thereof, thereby causing compression in the spring. Spring  82  is maintained in this manner when rock head  40  is inserted into pipe  24 , but as soon as rock head  40  exits pipe, the spring  82  returns to its original shape and position, thereby causing drill bit  60  is move in the opposite direction and into its second position. 
   A wheel  70  is preferably mounted onto the outside of each side wall  66  by way of a pin  72 . Wheels  70  are positioned to engage an interior surface  24   a  of pipe  24  so as to enable rock head  40  to be pushed or pulled more easily through bore  32  of pipe. Wheels  70  act as guides for rock head  40 , keeping it centered in pipe  24 . As may be seen from  FIGS. 4A &amp; 6A , wheels  70  extend at least partially beyond an outermost edge  42   c  of base  42  whether drill bits  60  are in a first expanded position ( FIG. 4A ) or in a second collapsed position ( FIG. 6A ). 
   Referring to  FIGS. 3-11 , rock head  40  is used in the following manner. Male hex connector  48  is inserted into female hex connector  50  on front end  22   a  of auger  22 . Hex connector  48  includes a first aperture  86  therein and hex connector  50  includes a second aperture  88  therein. When first and second apertures  86 ,  88  are aligned with one another, a connector pin  90  is inserted therethrough to lock hex connectors  48 ,  50  together and prevent them from inadvertently separating from each other. The connection made is secure enough to ensure that any rotational motion in auger  22  will be transmitted through to rock head  40  and that rock head  40  will not become detached as it bores through rock  30 . 
     FIGS. 4 ,  4 A &amp;  5  show rock head  40  in its second position, this being the configuration of the cutting head prior to its insertion into pipe  24  and after it has exited from pipe  24 . In this second position, the roller cones  60   b  of drill bits  60  extend at least partially beyond the outermost edge  42   c  of base  42 , thus causing rock head  40  to have an external diameter “A”. Diameter “A” is greater than the diameter “B” of the bore  32  of pipe  24 . When rock head  40  is in this second position with a portion of drill bits  60  extend beyond outermost edge  42   c , the first and second ends  82   a ,  82   b  of spring  82  are disposed a distance “C” apart from each other. 
   When rock head  40  is to be introduced into bore  32 , the diameter of rock head  40  has to be reduced. This is accomplished by moving or pivoting the body  60   a  of each drill bit  60  about retaining pin  80  ( FIG. 6A ). As body  60   a  pivots, the first and second ends  82   a ,  82   b  of spring  82  are compressed toward each other by the movement of front wall  66  toward inner wall  76 . This movement causes roller cone  60   b  of each drill bit  60  to move inwardly toward the central region  52  of base  42 , thus causing the overall outer diameter of rock head  40  to be reduced from “A” to slightly less than “B”. The pivotal movement of body  60   a  also places springs  82  under compression and allows wheels  70  to be brought into contact with the interior surface  24   a  of pipe  24 . 
   As boring machine  10  advances along tracks  12  toward soil-face  18 , it causes auger  22  to move through pipe  24 , pushing rock head  40  through the bore  32  thereof ( FIG. 8 ).  FIG. 7  shows the configuration of rock head  40  traveling through bore  32  of pipe  24 .  FIGS. 9 and 10  illustrate how the rock head exits pipe  24 . It can be seen that while the wheels  70  remain in contact with interior surface  24   a , the rock head  40  is in its first position with the roller cones  60   b  of drill bits  60  disposed proximate central region  52  of base  42 , i.e., drill bits  60  are in a compressed position. As soon as wheels  70  exit pipe  24 , springs  82  rapidly return to their original shape and position, thus causing body  60   a  of each drill bit  60  to move outwardly as is indicated by the arrows “X” in  FIG. 10 . Rock head  40  returns to its fully opened second position where the drill bits  60  extend at least partially beyond the outermost edge  42   c  of base  42 . In this position, rock head  40  can be used to bore through rock  30 . This is accomplished by boring machine  10  rotating auger  22 , which in turn rotates rock head  40 . 
   Referring to  FIGS. 11 and 12 , once a passageway  92  has been bored through rock  30 , then rock head  40  has to be removed and replaced with a dirt head  26  to cut through the soil disposed on the far side of rock  30 . In order to replace rock head  40 , boring machine  10  is withdrawn along tracks  12  toward the back side  14   a  ( FIG. 1 ) of excavation pit  14 . This causes auger  22  and rock head  40  to be withdrawn back into bore  32  of pipe  24 . As rock head  40  enters pipe  24 , wheels  70  cam against the end of pipe  24 , and slide into the bore  32 , sliding against interior surface  24   a  of pipe  24 . This camming action causes body  60   a  of drill bits  60  to pivot about retaining pins  80  and rotate inwardly toward central region  52  of base  42  ( FIG. 12 ). This effectively reduces the outer diameter of rock head  40  so that it is able to fit within bore  32  of pipe  24 . Auger  22  is withdrawn from pipe  24  and as rock head  40  exits pipe  24 , drill bits  60  pivot about retaining pins  80  and rock head returns to its second position. The hex connectors  48 ,  50  are then detached from one another and rock head  40  may then be replaced with dirt head  26 . 
   The springs  82  utilized in this device are manufactured to be strong enough to be compressed and expanded numerous times so that rock head  40  can be reused. Springs  82  are also sufficiently strong enough to withstand the rigors of boring through the rock. 
   It will be understood by those skilled in the art that rock heads in accordance with the present invention are sized to be used in conjunction with pipes of a defined range of internal diameters. Within that range of pipe diameters, the drill bits will pivot to a greater or lesser degree in order to be received within the bore of any one particular pipe. The drill bits do need to pivot to a degree sufficient to allow for forward or rearward motion of the rock head and auger through the pipe. If the fit is too tight so that travel through the pipe would be substantially hindered, then the boring company would employ a differently sized rock head in accordance with this invention. Consequently, the boring company would utilize a plurality of differently sized rock heads with a plurality of differently sized pipes. 
   In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
   Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.

Summary:
A rock head for use with an auger borer to bore a passageway through a body of soil and rock and simultaneously laying a pipe in that bored passageway. The rock head has a base connectable to the leading end of the auger. A plurality of movable mounts are provided on the base and a roller cone is secured to each movable mount. A spring is disposed between the movable mount and the base. The spring is compressed as the movable mount pivots the roller cones inwardly toward a central region of the base. This reduces the diameter of the rock head so that it can travel through the bore. Each movable mount is provided with at least one wheel so that it can ride smoothly through the bore. When the rock head exits the pipe, the springs automatically pivots each roller cone outwardly so that at least a portion thereof is disposed beyond the outermost edge of the base. In this second position, the rock head has a greater diameter than the pipe bore and therefore it cannot travel therethrough. When the auger is withdrawn through the pipe, the movable mounts pivot the roller cones from the second position back to the first position, thereby causing the rock head to collapse to a diameter sufficiently small enough to travel back through the pipe.