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RELATED APPLICATIONS 
     This application relates to and claims priority from U.S. Application Ser. No. 60/317,442 filed Sep. 7, 2001 entitled POWER SWIVEL, AIR DELIVERY SYSTEM AND ROTATING HEAD, the disclosure of which is hereby incorporated in its entirety by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to machinery and methods for exploring beneath the earth&#39;s surface and, more particularly, to stratigraphic exploration. 
     BACKGROUND OF THE INVENTION 
     One conventional technology useful for exploring the subsurface characteristics at a geological location includes the use of a cone penetrometer. This apparatus has a cone with an electronic stress sensor that is forced downward through the various subsurface layers. As the cone penetrates different strata, the data sensed by the cone is either collected in the cone or transmitted back to the surface. This data indicates characteristics and thickness of the different strata below the surface. 
     Recently, other technologies that fall into the general class known as “direct push” equipment have been developed to provide other data about subsurface conditions. One common technology of this nature is known as GeoProbe® and another is HydroPunch. 
     In practice, these direct push technologies, including the cone penetrometer, are delivered to a field site on some type of mobile platform such as a truck or track-mounted vehicle. The platform is relatively large and heavy in order to handle the forces applied, and support the equipment, involved in direct push techniques. A sensor, such as a cone, is attached to a section of pipe which is, itself, coupled using any of a variety of known means to a mounting system. Included in any of these different platforms are hydraulic rams that attach to this mounting system and produce the downward force needed to push a sensor (and attached piping) down through the ground. 
     The rams force the mounting system downward which forces the piping and sensor downward as well. As more piping is needed, the mounting system is detached from the top piping section, a new pipe segment is added, and pushing continues. For example, in cone penetrometry, each pipe segment is typically one meter long. 
     Even though direct push systems can generate up to 40,000 lbs of force, these systems are unable to penetrate or push sensors through consolidated or cemented layers below the surface. In the past, when a consolidated layer was reached, either the site data collection stopped or a conventional drilling rig was brought in to penetrate the consolidated layer. 
     However, the logistical difficulty in utilizing a conventional drilling rig makes this solution very problematic. An available rig has to first be found and then be delivered to the site. In preparation for the arrival of the drilling rig, the direct push equipment must be cleared from the site and the site prepared for the rig. Water collection ponds and other infrastructure is needed for the conventional drilling rig. Once the drilling operation is completed, the site must be cleaned-up and restored for the return of the direct push equipment. 
     Accordingly, there is an unmet need for methods and machinery useful with direct push equipment that allows drilling through consolidated surfaces that can be accomplished quickly, efficiently, economically and with as little disruption as possible at a field site. 
     SUMMARY OF THE INVENTION 
     The present invention addresses these and other needs by providing an air drilling swivel that works with any direct push equipment so as to provide drilling capabilities in the field without the presence of a conventional drilling rig. As a result, the use of direct push equipment is not significantly hampered when consolidated or cemented layers are encountered during subsurface exploration. Within the present application, the term “direct push” is used for convenience and is intended to encompass both conventional direct push equipment as well as driven, hammer driven, or driven-vibrating equipment. 
     One aspect of the present invention relates to a method for drilling. According to this aspect direct push equipment is used to push a first set of pipe sections and sensor down a bore hole. Then, the first set of pipe sections and sensor are removed from the bore hole and the direct push equipment. Next a power swivel is attached to the direct push equipment, along with a second set of pipe sections and drill bit; and then drilling is performed further down the bore hole with the power swivel. 
     Another aspect of the present invention relates to a power swivel for drilling down a bore hole. According to this aspect, the power swivel includes a stationary housing configured to be mounted to direct push equipment; a hollow rotating drive shaft configured to rotate within the stationary housing; and a set of hollow pipe sections. A far end of the pipe sections has a drill bit and a near end of the pipe sections is coupled with the rotating drive shaft such that the hollow region of each pipe section aligns with the hollow region of the rotating drive shaft. Within this arrangement, the stationary housing includes one or more air inlet apertures, and the rotating drive shaft includes one or more air openings and arranged within the housing. These different air openings are arranged so that, while the drive shaft is rotating, the one or more air openings periodically align with the one or more air inlet passages to provide a passage way for air into the hollow drive shaft. 
     Still other objects and advantages of the present invention will become readily apparent from the following detailed description, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
     FIG. 1A illustrates an exemplary direct push operation. 
     FIG. 1B illustrates an exemplary drilling operation according to an embodiment of the present invention. 
     FIG. 2 illustrates a more detailed view of the operation of FIG.  1 B. 
     FIG. 3 illustrates a flowchart of using embodiments of the present invention to drill with direct push equipment. 
     FIG. 4 illustrates a schematic view of an exemplary swivel according to embodiments of the present invention. 
     FIGS. 5A and 5B illustrate a detailed view of the swivel of FIG.  4 . 
     FIG. 6 illustrates a detailed view of an exemplary drive shaft useful in embodiments of the present invention. 
     FIG. 7 illustrates an exploded view of a drilling nipple and packoff according to embodiments of the present invention. 
     FIG. 8 illustrates an exemplary air delivery system according to embodiments of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     To aid with the explanation of the present invention, concrete examples have been given of borehole size, drill rod size, equipment names and drilling environments. The present invention is not limited to these and other specific cases provided herein which, instead, are give only by way of example to aid in the understanding of the present invention. 
     FIG. 1A depicts a schematic view of direct push equipment being used in the field. The specific details of the equipment platform  101  (e.g., truck, track-mounted vehicle, etc.) are not shown as the platform involves conventional direct push equipment and which is known in the art. 
     Within the equipment platform  101 , there is a mounting plate  102  that is coupled with one or more pipe sections  104 . These multiple pipe sections  104  descend below the surface of the ground  106  and end with a tip section  108  that includes a sensor or other electronic/sampling equipment. The hydraulic ram or rams  110  is coupled with the mounting plate  102  to provide the downward force needed to push the tip or sampling device  108  through the ground  106 . 
     Although depicted as a simple block diagram in FIG. 1A, the hydraulic ram  110  is typically plural hydraulic rams that are evenly located around the mounting plate so as to provide sufficient and evenly distributed downward pressure. The hydraulic ram  110  also provides the upward force needed to raise the plate  102  in order to add new pipe sections  104  and to raise the pipe sections  104  when the tip  108  needs to be removed from the ground. 
     The arrangement of FIG. 1A will result in the tip sampling equipment  108  being pushed through the ground  106  until a layer is reached that is consolidated, or cemented, and proves too hard to penetrate with direct push technology. 
     FIG. 1B depicts a schematic view of the power swivel  120  attached to the mounting plate  102  and hydraulic rams in accordance with embodiments of the present invention. The power swivel  120  is attached in this manner so that a consolidated layer  122  can be drilled through. Within the field of drilling, in general, a swivel is a mechanical device that simultaneously suspends the weight of a drill string and provides for the rotation of the drill string beneath it. A swivel includes a stationary part, that is coupled with a power source (e.g., a hydraulic motor) and a mounting platform, and a rotating part that is coupled with a drill string. Conventionally, a swivel also permits a high-volume flow of drilling mud or air from the stationary part through to the rotating part without leaking. 
     The specific type of hydraulic motor is not critical to the present invention; however, one exemplary motor having sufficient capacity to be effective is the DANFOSS OMS 80 151F500 3. 
     Instead of the sensor tip  108  used in the direct push configuration of FIG. 1A, the drilling arrangement of FIG. 1B includes a drill bit  126  fixedly attached at the end of the drill string comprised of multiple drill pipe sections  124 . A hydraulic source provides input to a hydraulic motor  130  that powers the swivel  120 . As the hydraulic motor  130  causes a drive shaft of the power swivel  120  to rotate, the drill string  124  rotates causing the drill bit  126  to rotate and cut through the consolidated layer  122 . Typical size bore holes would range from 1.25 inches in diameter to 6.25 inches in diameter; although larger scale equipment could be used to produce larger holes. 
     In the arrangement of FIG. 1B, the power swivel  120  is rigidly and securely attached to the mounting plate  102  and hydraulic rams. Similarly, sections of drill pipe  124  are connected to the power swivel  120 . In this manner, the hydraulic ram&#39;s action to force the plate  102  downwards (or upwards) is transferred through the power swivel to the drill pipe sections  124 . As a result, the drill bit  126  rotates and is pushed through the layer  122  to effect drilling of that layer. By utilizing the direct push platform, that includes hydraulic rams, hydraulic fluid, mounting plates, etc., drilling through consolidated layers is performed without the need to bring in a conventional drilling rig with all the accompanying difficulty. 
     As shown in FIG. 1B, the power swivel  120  also includes an air inlet  132  that receives an air flow from a source  134 . The details and utilization of this air inlet  132  is depicted more clearly in FIG.  2 . 
     FIG. 2 shows a more detailed view of the power swivel  120  but, so as not to obscure these details, omits some of the equipment depicted in FIGS. 1A and 1B. In particular, there is a circuitous flow path (illustrated by the arrows) in the drilling arrangement of FIG. 1B that allows air, or other fluids, to be introduced at the power swivel  120 , flow through the power swivel  120 , enter the pipe string  124 , flow through the pipe string  124 , exit through the drill bit  126 , enter the bore hole, and then exit above ground thereby removing drill cuttings from the borehole. 
     An air source  202  is connected to the power swivel  120 , typically through some type of nipple  204 , to produce sufficient air flow to permit drilling. An exemplary air source could be the SULAIR 185H Air Compressor. Additives (e.g., water, surfactants, foam, etc.)  206  can be added to the air flow into the power swivel  120 . The proper use of additives according to different drilling conditions encountered in the field is known to a skilled artisan and can be used to improve drilling efficiencies and rates. 
     The air flow enters the power swivel  120  and is directed downwards toward the pipe string  124 . The pipe sections of the pipe string are hollow and permit the air flow to proceed towards the drill bit  126 . The drill bit  126  has exit holes, similar in size to the inside diameter of the pipes in the pipe string  124 . The air exiting the drill bit  126  enters the borehole  208  and lifts the cutting towards the surface. For example, the drill bit  126  can be approximately 2.5 inches in diameter while the pipes have an outside diameter of nearly two inches. This difference in sizes creates an annular region that permits the air to flow upwards unrestricted but that is not so large as to result in a large loss of velocity. Upon nearing the surface, the air flow is redirected by an air nipple  210 . 
     The air nipple  210  includes a portion  214  that is ideally the diameter of the borehole  208 , or at times even larger, and is inserted into the top of the borehole  208  to a depth of approximately 2 to 3 feet or more, for example. The air nipple includes a flange  216  and an annular elastomeric packoff  212 . The annular packoff  212  forms a seal around the drill pipe  124  that is inserted through the opening of the air nipple  210 . The air nipple  210  also includes an exit aperture  218 , known as a blewie line, that allows air flow and cuttings to exit the borehole  208  and acts to direct the exit flow in a desired direction. The air nipple  210  is located at a depth such that the exit aperture  218  is approximately 6 to 18 inches from the surface of the ground  106 . A collection apparatus (not shown) can be connected with the aperture  218  to collect cuttings for further analysis and to filter the exiting air flow to prevent detrimental air quality near the drilling site. 
     In operation, the air flow in the borehole  208  rises until it reaches the air nipple  210 . The air flow then enters the annular region formed between the section  214  and the drill pipes  124 . The air flow then exits out the exit aperture  218 . 
     FIG. 3 depicts a flowchart of an exemplary method of utilizing the power swivel  120 . According to the flowchart, subsurface exploration begins, in step  302 , with operating the direct push equipment in a normal fashion. This operation continues until step  304  when a consolidated or cemented layer is encountered. At this point direct push operations cannot continue. 
     Accordingly, the pipes that have been attached to the direct push sensors or sampling device are removed, in step  306 , one-by-one from the hole in preparation for drilling. Once the direct push sensors or sampling devices and pipes are removed, the power swivel can be attached, in step  308 , to the mounting plates and hydraulic rams of the direct push platform. As the power swivel weighs about 100 lbs, it can be maneuvered into place by personnel at the drill site either manually or with mechanical assistance. Attachment of the power swivel also includes connecting the power swivel (and hydraulic motor) to a hydraulic source and an air source. 
     Next, in step  310 , the drill bit and sufficient piping to reach the bottom of the borehole are coupled together and lowered into the borehole. However, before this step is started, an air nipple and pack-off are inserted into the borehole so that the air flow properly exits from the borehole during drilling. 
     In step  312 , the drill string and the power swivel are connected together so that the drilling operation, in step  314 , can take place. The drilling operation continues until the consolidated layer is penetrated. 
     After drilling is completed, the drill bit, piping and power swivel are removed from the direct push platform in step  316 . Afterwards, the direct push sensor, drill pipes and equipment are re-installed, in step  318 , so that the direct push operation can continue if desired. 
     Preferably, the same piping can be used in either direct push operation or in drilling operation. One requirement being that the drilling piping needs to have a hollow core to allow air flow of a sufficient volume to permit removal of the cuttings from the bottom of the borehole. 
     In an alternative scenario, all the strata of interest may be below a known consolidated layer. In this scenario, it is not necessary to start with a direct push operation until reaching that consolidated layer. Instead, drilling can commence from the surface, using the power swivel, and only after the desired stratum has been reached will the direct push equipment be lowered into the borehole. 
     A high-level illustration of the power swivel according to one embodiment is depicted in FIG.  4 . According to this embodiment, the power swivel includes a number of features that improve its reliability, ease of use and maintenance. Furthermore, one of the critical elements when air drilling is maintaining a sufficient air flow through the flow path. The power swivel of FIG. 4 is designed so that air flow is not restricted into the drill string which results in a large volume of air flowing through the drilling system without the build-up of high pressures. In practice, the present power swivel design enjoys internal pressures typically less than 125 psi. 
     The hydraulic motor  402  is not specifically a part of the power swivel but is depicted in FIG. 4 to show its relation to the other parts. The swivel  400  includes a number of major sub-assemblies as shown in FIG.  4 . Near the motor  402 , is the planetary gear assembly  404 , this gear assembly reduces the RPMs of the motor  402  to spin the drive shaft  406 . Typically, the drive shaft rotates between 0 and 60 RPMs. The drive shaft  406  engages a splined shaft  414  so that when the shaft  406  rotates so does the splined shaft  414 . The other end of the splined shaft  414  is operatively coupled with a connecting piece  418  to which a drill string (not shown) is connected. The spinning spline shaft  414  causes the connecting piece  418  to spin which, in turn, rotates a drill bit at the end of a drill string (not shown). 
     Part of the planetary gear  404 , the drive shaft  406  and a portion of the spline shaft  414  are surrounded by a housing  408 . During drilling operations, these assemblies rotate within the housing  408  while the housing  408  remains stationary. Although not drawn to scale in FIG. 4, the housing  408  includes mounting flanges  416  which are attached to the direct push platform. Through these flanges  416 , the hydraulic rams of the direct push platform are able to exert downward pressure on the housing  408  and a drill string connected thereto. The drill string is forced downwards in the borehole, typically at a range of 0 to 5,000 lbs, while the drill string is rotating. The hydraulic rams also exert an upward force when the drill string needs to be raised. 
     The external splines on the splined shaft  414  mate with internal splines on the drive shaft  406  in such a way as to permit the spline shaft  414  to move upwards within the opening of the drive shaft  406  to facilitate adding or removing pipe sections to the connecting piece  418 . Also, an O-ring or other means (not shown) is included near the top of the spline shaft  414  so that a tight seal is maintained with the drive shaft  406 . 
     The airflow through the power swivel is unrestricted because of the alignment and size of holes  410  and  412  as well as the hollow nature of the rotating components. Holes  410  in the housing  408  are used (typically with a nipple) to introduce air from an external air source into the swivel  400 . The holes  412  in the drive shaft  406  allow the air to enter the inside of the rotating portion of the swivel  400 . As the drive shaft  406  rotates, one of the holes  412  regularly aligns with the housing hole  410  to create an unrestricted path for air to flow. Conventional drill pipes have an internal diameter of approximately one square inch, although larger (or smaller) sizes are also useful. Thus, the airflow through the holes  410  and  412  of the power swivel  400  should also provide for a full square inch of air to match the inner diameter of the pipe string. By providing this unrestricted airflow, the swivel  400  will allow faster drilling as the large air volume will be able to quickly complete its circuit and remove any cuttings from the borehole. 
     The embodiment of FIG. 4 depicts four holes  412  spaced at 90 degrees around the drive shaft  406  and two holes  410  opposite each other on the housing  408 . Preferably, the holes  412  are roughly one inch square while the holes  410  are slightly larger at approximately 1.3 to 1.4 square inches. Other sizes, numbers, and placements of these holes are also contemplated which provide the equivalent unrestricted air flow throughout the swivel  400 . 
     Both holes  410  do not need to be used simultaneously; doing so only increases the volume of air available for drilling. If one hole  410  is not being used, then it can be plugged. 
     FIGS. 5A and 5B illustrate a side view and a cutaway view, respectively, of a particular embodiment of a power swivel. There are elements of the power swivel  500  that are conventional items such a O-rings, bearings, bolts, etc. that are used in a conventional manner and, although shown in the figures, are not discussed in great detail. 
     Starting at the top of the swivel  500  shown in FIG. 5A, there is a flange  502  which is useful for attaching the planetary gears, the hydraulic motor and the swivel  500  together. The flange  502  is merely the bottom portion of the planetary gear while the remaining portion of the gear above the flange is not shown in this figure. An air inlet nipple  504  is shown on both sides of the housing  506  which is also known as a case weldment assembly. This housing  506  remains stationary during operation of the swivel  500  while other sub-assemblies housed inside rotate. 
     Below a middle flange of the housing  506 , is a retractable cover  508  that permits access within the housing  506  without requiring disassembly. In reference to FIG. 5B, flexible packing  534  is depicted near the top of the swivel  500 . This packing can be, for example, Thermabraid™ packing which is flexible graphite, and will eventually wear down over the lifetime of the swivel  500 . Adjustment screws are accessible though the opening behind the cover  508  that enable tightening of the surfaces around the flexible packing  534 . By tightening the pressure on the packing  534 , its useful lifetime can be extended as compared to packing which needs replacing when it beings showing signs of wear. 
     Returning to FIG. 5A, attached to the housing  506 , using bolts  512 , is a flange mounting assembly  510 . This assembly  510  is the part of the swivel  500  which is mounted on the direct push equipment during drilling. 
     The spline shaft  514  exits from the bottom of the housing  506  and couples with a transition, or extension, piece  516  connected to the end piece  518 . The tip of the end piece  518  is threaded to mate with conventional drilling piping. 
     The top of FIG. 5B is similar to that of FIG. 5A in that a portion  530  of the planetary gear is depicted. Within FIG. 5B, there are also a number of O-rings (e.g.,  528 ,  542 , and  554 ) that provide for fluid tight seals between adjacent surfaces. These seals help ensure that the air flow through the power swivel  500  is not diminished by leaks. 
     Similarly, there are screws (e.g.,  520 ) and bolts (e.g.  522 ) that are used in their conventional manner to fixedly attach two adjoining surfaces such as the lock plate  526  to its mating surface. There are also a number of elements that are arranged in the annular region between the stationary swivel housing  506  and the rotating drive shaft  548 ; these elements support the smooth operation of the power swivel but other, functionally equivalent substitutes are contemplated and considered to be within the scope of the present invention. Some of these support elements include the union cylinder  536 , the disc spring  538 , a washer  540 , the union bearing  546  and the casing bearing  552 . 
     The planetary gear  530  has a rotating shaft that is splined on its external face. The drive shaft  548  has a region near its top that has splines on its internal face. While it is possible that these two splines can be arranged so that they mate and engage each other during operation, the preferred embodiment of FIG. 5B includes a spline bushing  532 . This bushing  532  has splines on both its internal and external faces. The splines on the inside of the bushing engage the shaft of the planetary gear and the splines on the outside of the bushing  532  engage the inside of the drive shaft  548 . FIG. 6 shows a more detailed view of the drive shaft  548 . The splines  602  near the top are what mate with the spline bushing  532 . The center section  606  is preferably smooth on the inside as this portion does not need to mate with any other surfaces. The bottom section  604  (although not visible from this perspective) includes internal splines that engage the spline shaft  514 . A plug  544  fits within the drive shaft  548  below the splined section to prevent air from exiting from the top of the swivel  500 . 
     In operation, the drive shaft  548  rotates at approximately 0 to 60 RPM while the drilling bit is being driven down the borehole. Just as importantly, though, the holes  608  of the drive shaft  548  regularly rotate in front of the air inlets in the housing  506  so that air enters the swivel  500  in an unrestricted manner. 
     Two important elements of the swivel  500  are thrust bearing  524  and tapered roller bearing  550 . The thrust bearings  524  keep the thrust from being transferred in an upward motion to the gear train and prevent downward thrust from being transferred to the housing. As a result, wear and tear on the machinery will be significantly reduced which saves maintenance time and costs. The tapered bearing  550  acts as both a thrust bearing (similar to  524 ) and as an axial thrust bearing. In other words, this bearing  550  also helps eliminate lateral wear on the packing and housing of the swivel thereby eliminating vibration and lateral movement. 
     Drilling Nipple and Packoff 
     FIG. 7 depicts a detailed view  700  of the drilling nipple and packoff whose operation was explained in relation to FIG.  2 . In a preferred embodiment, this device  700  is composed of a steel tube  702  approximately 2.5′ in length having an internal diameter of approximately 3 inches and an outside diameter of about 3.5 inches. The tube  702  can be constructed from cold rolled steel or other equivalent materials. The lateral opening  704  forms approximately a 90 degree bend with the tube  702  and is around 8 inches from a flange  705 . The flange  705  is part of the tube  702  and has a center hole with a 3 inch diameter and a larger outside diameter such as, for example, 6 inches. There are multiple holes through the flange  705  to permit the pipe wiper  706  and top flange  708  to be secured to the flange  705 . The pipe wiper  706  can be similar to a one inch pipe wiper manufactured by A. W. Rubber, Inc. that acts as a sealing element between a drilling borehole and push/drill rods or pipes. The top flange  708  also has a three inch inner diameter and a larger outer diameter, such as 8 inches. 
     Air Delivery System 
     As mentioned earlier, the power swivel preferably provides air drilling adapted to a variety of push equipment. One embodiment of an air delivery system for the power swivel is depicted in FIG.  8 . The air delivered to the power swivel flows through the drilling system in an unrestricted manner such that a full inch of air flow is supported during drilling operations. The embodiment of FIG. 8 is described within the specific environment of providing a full square inch of air flow through the power swivel. If different air volumes are desired, different dimensioned equipment can be readily substituted. 
     An air compressor  802  is used to provide an external source of air into the air delivery system  800 . The compressor  802  is connected to a fitting  804 , such as a 1.00″ NPT×1.25″ Chicago fitting, that is connected to a section of pipe  806 , such as 1″ extra-heavy steel piping. A Sensor  808  can be included to sense and indicate pressure conditions before the valve  810 . Valve  810  is a 1.25″ NPT, normally closed, remotely operated valve and is connected by the pipe section  811  with a 1.25″ NPT, normally open, valve  814 . 
     The valves  810  and  814  can be solenoid valves or pneumatic valves or even other equivalent valve mechanisms. The valve  810  is used to control and shut off the air supply to the swivel. In the case of a power failure or an emergency, the valve will automatically close to shut off the air supply. In the event of an emergency, valve  814  will open to discharge unrestricted to the atmosphere. This is to release pressure from the piping system. In normal operating mode, the valve  814  can be controlled to release to the atmosphere so as to relieve pressure in order to permit addition or removal of additional rods from the drill string. Both valves  810  and  814  are controllable from a control panel  812  in the drill equipment operator&#39;s station. 
     The precise placement of sensors  808  and  816  on their respective piping segments is not critical as long as sensor  808  is placed before the valve  810  and sensor  816  is placed after the valve  814 . These sensors are used to sense pressure within the air delivery system and provide this data to the drill operator. 
     The end of the air delivery system  818  connects (preferably using some type of quick connect coupling) to a flexible high-pressure delivery line (not shown). The delivery line is connected with the swivel thereby providing air for the drilling operation. 
     The various embodiments of the swivel described herein have usually been described in the environment of air drilling because air drilling has a number of advantages over fluid drilling. However, the present invention can utilize water, or mud, drilling techniques as well. Similarly, mist drilling, foam drilling and other drilling techniques are contemplated for use with the present invention. The use of air flow, however, eliminates contaminated drilling fluvias being raised to the surface, significantly reduces the potential for contamination of underground aquifers through filtration of free water in the mud system, and enables drilling in freezing weather. 
     Although the present invention has been described and illustrated in detail, it is understood that the same is by way of illustration and example only, and is not to be taken as a limitation, in scope or spirit, of the present invention which is limited only by the terms of the appended claims.

Summary:
A power swivel provides the rotational force to drill consolidated subsurface strata while an unrestricted airflow through the swivel and down a drill string remove cuttings from the borehole. The power swivel is configured to mount on direct push/driven-vibrating equipment, such as a cone penetrometer, to eliminate the need for a conventional drilling rig when a consolidated layer is encountered during direct push/driven-vibrating operations. A drilling nipple and pack-off are provided near the surface to maintain the air flow during drilling and to direct the cuttings to a desired location. Also, a dual-valved air delivery system provides safe, remote-controlled air flow to the swivel.