Lubricated pilot tubes for use with auger boring machine pilot steering system and use thereof

A pilot tube for an auger boring machine has a lubrication through passage formed therein through which water or another lubricant may be pumped during the driving of the pilot tube to facilitate formation of a pilot hole in the earth which is subsequently followed by an auger in forming a trenchless hole for laying underground pipe. Preferably, the lubrication passage extends to exit openings adjacent or on a steering head. A lubrication feed swivel is connected the trailing end of the pilot tube for feeding the water into the pilot tube while allowing rotation of the pilot tube for the steering thereof during the process of driving the pilot tube.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates generally to an auger boring machine and a method of use in the trenchless installation of underground pipe. More particularly, the invention relates to such a machine which utilizes a pilot tube for forming a pilot hole for guiding the auger of the machine. Specifically, the invention relates to a lubricated pilot tube and drive assembly used in forming the pilot hole.

2. Background Information

The use of an auger boring machine for installing underground pipe between two locations without digging a trench there between is broadly known. In addition, it is known to use a pilot tube formed of a plurality of pilot tube segments to create a pilot hole for guiding an auger which bores a larger hole so that the auger remains within a reasonably precise line and grade. For example, see U.S. Pat. No. 6,206,109 granted to Monier et al. However, it requires an enormous amount of force to drive the pilot tube through the ground due to frictional engagement between the pilot tube and soil, as well as to the pilot tube's inherent compacting and displacement of soil. Thus, there is a need in the art to minimize the difficulties associated with these effects. The present invention solves this and other problems in the art.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an apparatus comprising: an auger boring machine pilot tube having leading and trailing ends and adapted for being driven into the earth to form a pilot hole to be followed by an auger; and at least one lubrication through passage formed in the pilot tube from adjacent the trailing end to adjacent the leading end.

The present invention further provides a method comprising the steps of: driving a pilot tube having leading and trailing ends into the earth to form a pilot hole therein adapted for guiding an auger; and moving water from the trailing end toward the leading end through a lubricant through passage formed in the pilot tube during the step of driving.

DETAILED DESCRIPTION OF THE INVENTION

The auger boring machine of the present invention is indicated generally at10inFIGS. 1 and 2. Referring toFIG. 1, machine10is typically disposed in a pit6formed in the earth's soil or ground8and configured to bore a hole through ground8for the purpose of laying underground pipe in the bored hole. Machine10typically bores a hole from within a pit such as pit6to another pit which may be spaced several hundred feet away. Machine10includes a lubrication system for pumping a lubricant such as water through the pilot tube and steering head in order to facilitate formation of the pilot hole. Machine10includes a frame12which extends from a front end14to a rear end16of machine10. Front and rear end14and16define there between a longitudinal direction of machine10. Machine10further has first and second opposed sides18and20(FIG. 2) defining there between an axial direction of machine10.

An engine compartment22is mounted on frame12and houses therein a fuel powered engine24, an electric generator26powered by engine24and a hydraulic pump28also powered by engine24. An auger drive compartment30is disposed in front of compartment22and houses therein an auger drive having a rotational output shaft32for rotationally driving an auger34(FIG. 18). Frame12further includes a pair of spaced longitudinally extending rails36secured to a plurality of cross bars38which are mounted on ground8in the bottom of pit6. A pair of adjustable stabilizing poles40are telescopically received in and adjustably mounted respectively on rails36and configured to press against the wall of ground8which bounds pit6.

A pilot tube guidance and drive assembly42is removably mounted on frame12and more particularly on rails36via mounting legs44which are removably insertable into openings46formed in each of rails36. Mounting legs44and the mounting mechanism of which they are a part are described in further detail in the copending application entitled Pilot Tube System And Attachment Mechanism for Auger Boring Machine which is incorporated herein by reference and filed concurrently herewith. Assembly42when mounted on frame12is positioned so that a central longitudinal axis X of a cylindrical pilot tube48is coaxial with a longitudinal axis Y which passes centrally through output shaft32and about which shaft32is rotated when driving auger34. Assembly42includes a generally circular rear plate50which abuts compartment30when assembly42is mounted on frame12and includes a portion which is inserted into compartment30to assist with the alignment of assembly42.

Referring toFIGS. 3-4, assembly42includes front and rear mounting assemblies52and54which also serve as supports providing rigid structure extending axially across the width of assembly42. Assemblies52and54are seated on rails36of frame12when assembly42is mounted on frame12. A pair of longitudinally extending parallel spaced rails56and58are rigidly mounted on assemblies52and54and extend along most of the length of assembly42. Adjustable stabilizing poles60are telescopically mounted respectively within first and second rails56and58and are adjustable to provide force against ground8in the same manner as poles40.

A rigid front cross member62extends between and is connected to each of rails56and58adjacent the front thereof with a front pilot tube support64mounted thereon centrally between rails56and58. Support64includes a plurality of bearings which engage the pilot tube48to allow longitudinal movement of tube48as well as rotational movement of tube48about axis X to allow for the steering thereof. Rear plate50and associated structure attached thereto serve as a rear cross member for rigidly connecting rails56and58to one another at the rear of assembly42. An intermediate cross member66extends axially between rails56and58and is supported respectively on rails56and58by first and second roller assemblies68and70(FIG. 12). Each roller assembly includes a pair of longitudinally spaced upper rollers72and longitudinally spaced lower rollers74which respectively rollingly engage upper and lower surfaces76and78of respective rails56and58. Upper and lower surfaces76and78are parallel surfaces which extend longitudinally from the front of rails56and58to around the midway point between the front and rear of said rails. An electric guidance control motor80is mounted on cross member66for selectively rotating pilot tube48in either direction about axis X.

In accordance with a feature of the invention, a lubricant feed swivel82having a lubricant inlet84is mounted on motor80by a pair of spaced mounting rods86extending forward from motor80. Swivel82is connected to pilot tube48and thus serves as an engaging member for drivingly engaging tube48during operation of assembly42. As shown inFIG. 4, inlet84of swivel82is in fluid communication with a lubricant feedline85which is in fluid communication with a source87of lubricant, which is typically water. Source87includes a pump for pumping water. Swivel82receives water through inlet84to pump the water through pilot tube48and through a steering head88connected to the front of pilot tube48, the water flowing out a forward exit opening90and a plurality of lateral exit openings92. Swivel82is described in greater detail further below.

A crane stand94is mounted on the frame of assembly42for supporting a crane (not shown) used for lifting pilot tube segments into position for connecting the various segments to form pilot tube48during the process of jacking or driving tube48to form the pilot hole. A cord carrier96is mounted atop rail56and includes a plurality of links98which are pivotally connected to one another so that electrical cords101(FIG. 4) will not become tangled during the longitudinal driving of pilot tube48. A support arm extends from cross member66to one of links98to provide support to the upper section of carrier96. Electrical cord101is electrical communication with motor80and generator26.

During the jacking or driving of pilot tube48, a steering mechanism keeps tube48on line and grade using a theodolite which utilizes a camera100(FIGS. 2,13) in electrical communication with a display monitor102which displays the view of the camera through pilot tube48of an illuminated LED target104(FIGS. 9-10) disposed within pilot tube48adjacent steering head88. In order for camera100to view LED target104, pilot tube48is hollow, as are the other structures intermediate camera100and target104, such as motor80and swivel82, in order to provide a line of sight Z (FIGS. 5,8,9,11) passage between camera100and target104. A guidance control unit106is mounted on rail58and includes manually operable controls108typically in the form of joysticks in electrical communication with motor80in order to send a signal to motor80to control rotation of pilot tube48.

Assembly42includes a continuous stroke drive mechanism110comprising a pair of hydraulic actuators in the form of piston-cylinder combinations112powered by pump28(FIG. 1). Each combination112includes a cylinder114and a piston116slidably received therein. Each cylinder114is mounted on the rear cross member adjacent plate50while each piston116is mounted on intermediate cross member66. Pistons116extend and retract simultaneously along paths that are parallel to one another and substantially parallel to axis X of pilot tube48. Combinations112must provide a substantial amount of forward and reverse thrust. For example, the forward thrust produced by combinations112on one preferred embodiment has a maximum thrust of 280,000 pounds while the reverse thrust has a maximum thrust of 140,000 pounds. Combinations112are capable of a continuous stroke throughout the extension thereof and likewise during the retraction thereof. Drive mechanism10and other suitable drive mechanism s are described in further detail in the copending application entitled Method And Apparatus For Providing A Continuous Stroke Auger Boring Machine which is incorporated herein by referenced and filed concurrently herewith.

Pilot tube48is made up of a plurality of pilot tube segments which are connected end to end to sequentially increase the length of pilot tube48during the jacking process. Typically, all or nearly all of the pilot tube segments are of the same length and are interchangeable with one another. However, some of the pilot tube segments may be of a different length, such as the lead pilot tube segment122, which is connected to steering head88and which is shorter than the standard pilot tube segments124connected sequentially behind segment122. Lead pilot tube segment122has a length of roughly two feet while pilot tube segments124typically come in lengths of five feet although this may vary. More particularly, tube segments124have an end to end length L1(FIG. 10) measured between the leading and trailing ends126and128thereof. While length L1is typically five feet as noted above, the tube segments may have a length of three feet, four feet or greater than five feet. If the lengths of the pilot tube segments are too short, they may became less practical for various reasons while tubes reaching greater lengths may become less desirable due to the substantial weight of the tubes and the additional length of the boring machine and the pit required for positioning the machine therein.

As noted previously, and in accordance with the invention, pilot tube48is configured to allow a lubricant such as water to flow therethrough to steering head88. The various structures including lubricant passages of pilot tube48are discussed with reference toFIGS. 5-7. More particularly,FIG. 5shows a sectional view of a pilot tube segment124which in part shows the lubricant passages therethrough. Tube segment124is formed of a heavy duty metal with sufficient strength to withstand the thrust forces noted earlier. Segment124has first and second coupling ends or members130and132having a mating configuration with one another so that a first coupling member130of tube segment124may be coupled to a second coupling member132of another tube segment124to form pilot tube48during the process of driving the pilot tube. Members130and132are respectively connected at either end of a central section134by welds, which are indicated generally at136in various places. Central section134includes an outer pipe135and inner pipe166. Each of outer pipe135and coupling members130and132have an outer diameter D1(FIG. 7) which is also the diameter of pilot tube48. In the exemplary embodiment, diameter D1is about 5.0 inches although pilot tubes having a diameter of 4.5 inches are common and the diameter typically ranges from 4 inches to 6 inches. First coupling member130includes an externally threaded end portion138stepped inwardly from the outer surface defining diameter D1thereof. Six lubricant passages140are formed in first coupling member130and extend from a leading end142thereof to a trailing end144thereof. Passages140are circumferentially equally spaced from one another as shown inFIG. 12. Each passage140has a counter bore adjacent end144in which a respective seal146is disposed. A central hexagonal opening148extends inwardly from trailing end144with passages140disposed radially outwardly thereof.

Second coupling member132includes an inner member150and an outer member in the form of an internally threaded collar152which is rotatably mounted on inner member150and configured to threadably engage the threaded portion138of a coupling member130of another pilot tube segment124. Inner member150has a leading end154and a trailing end156and includes a hexagonal segment158which is receivable within and has a mating configuration with hexagonal opening148of first coupling member130. Inner member150includes an annular wall160which is connected to a trailing end of segment158and extends radially outwardly therefrom. Wall160has a leading end161which extends perpendicular to segment158. A central passage162extends from leading edge154to trailing edge156and six lubricant passages164are disposed radially outwardly of passage162and are circumferentially evenly spaced from one another in order to align with passages140when a first and second coupling member130and132are joined to one another.

Inner pipe166defines a central passage158which communicates with passage162and opening148so that a through passage is formed in segment124extending from leading edge126to trailing edge128thereof. Inner pipe166is connected to inner member150and first coupling member130in a manner to provide an annular lubricant passage170between inner pipe166and outer pipe135.

Passage170communicates with the trailing ends of lubricant passages164and the leading ends of lubricant passages140in order to provide a lubricant passage through pilot tube segment124from leading edge126to trailing edge128. Other than the communication of passage170with passages164and140, passage170is sealed so that it does not communicate with central passage168or to the outer surface of outer pipe135. Passages162and168and opening148provide for line of sight Z extending therethrough along which camera100is able to view LED target104.FIG. 8shows two pilot tube segments124connected via the coupling of members130and132via the threaded engagement there between. Passages140are aligned respectively with passages164with seals146performing a seal against leading end161of inner member150.

FIG. 9shows additional passages in pilot tube48allowing for a flow of lubricant therethrough to steering head88. More particularly,FIG. 9shows that lead pilot tube segment122includes a first coupling member130which is connected to a second coupling member132of a pilot tube member124to align the respective passages thereof. Unlike pilot tube segment124, segment122is shorter and configured to carry target104therein, and thus does not include an annular central passage such as passage170of segment124. Instead, six lubricant passages172are formed therethrough in a manner similar to passages140and passages164in order to allow communication with passages140of coupling member130. However, passages172are positioned slightly radially outwardly of the respective passages140due to the increased diameter of a central passage171formed in lead pilot tube segment122for accommodating therein target104. Thus, passages172adjacent the respective trailing ends thereof extend radially inwardly at short sections173thereof. Likewise, passages172extend radially inwardly at the respective leading ends thereof at short sections175.

Passages172merge into a central chamber174formed in the rear portion of steering head88via respective passages176which extend radially outwardly from chamber174and communicate with sections175. Several other passages are formed in steering head188downstream of central chamber174which communicate with the outer surface of steering head88via exit openings90(FIGS. 3,4,14) and92. More particularly, a central passage177extends forward from chamber174and splits into four lateral passages178A-D (FIGS. 9-9A) and a forward passage179. More particularly, each of passages178and179branch off from a central chamber181immediately downstream from passage177. As shown inFIG. 9, passage178A angles upwardly and rearwardly from chamber181to the outer surface of steering head88and passage178B angles downwardly and rearwardly from chamber181to the outer surface of steering head88. As shown inFIG. 9A, passage178C extends laterally and rearwardly from chamber181to the outer surface of steering head88toward one side of head88and passage178D angles laterally outwardly and rearwardly from chamber181to the outer surface of steering head88on the opposite side from passage178C.

Steering head88has a maximum diameter at the location indicated at183inFIG. 9and tapers rearwardly and inwardly at a tapered section185. Each of passages178communicates with the outer surface of steering head88at respective openings92formed in tapered section185and thus behind the maximum diameter region183. Front passage179is centered as viewed from above inFIG. 9Aand angles forward and downwardly from chamber181as shown inFIG. 9through the outer surface of steering head at opening90. More particularly, steering head88has a leading tip187(FIGS. 9A,14) and a flat and generally oval shaped forward-facing steering face189which is configured to engage soil8and facilitate steering of pilot tube48therethrough when rotated by motor80. Steering face189angles rearwardly from tip187to an opposite side of steering head88to terminate at maximum diameter region183. Opposite steering face189, steering head88has a straight outer surface191which is substantially parallel to the outer surface of pilot tube48and a path of travel of tube48when being driven. Thus, opening90is formed on steering face189adjacent and rearwardly of tip187. Steering head88further includes a neck193which is stepped inwardly from tapered section185and disposed within passage171of pilot tube segment122. A pair of annular seals195make a seal between neck193and the inner surface of segment122defining passage171respectively forward of and rearward of passages176. A plurality of bolts197threadably engage neck193to secure steering head88to the front of tube segment122.FIG. 9further shows that lead tube segment122defines a central passage providing for line of sight Z therethrough to provide a clear view of illuminations180(FIG. 10) of target104.

FIG. 11shows a sectional view of the lubricant feed swivel82and portions of motor80along with the connecting members associated therewith.FIG. 11illustrates a central passage through motor80, swivel82and the connecting structure associated therewith so that line of sight Z is maintained.FIG. 11also illustrates the initial portions of the lubricant passage within pilot tube48and the connection of swivel82. More particularly, feed swivel82includes a stationary annular housing182which is mounted on a stationary housing184of motor80via rods86(FIG. 3) which are mounted on an annular flange203of housing184. Swivel82also includes a rotatable portion186which is connected to a rotatable drive188of motor80to rotate therewith. Portion186is rotatably mounted within housing182by a pair of longitudinally spaced ring bearings190with a pair of spaced annular seals192disposed between bearings190and respectively abutting said bearings. V-pack seals have been found to work well in this application although seals192may be any seal suitable for the purpose. A pair of annular retaining clips205are disposed respectively in front of the forward bearing190and rearwardly of the rear bearing190respectively in abutment therewith to retain bearings190in position. Rotatable portion186includes a threaded portion207adjacent its trailing end which threadably engages the internal threads of a coupling collar209which is mounted on rotatable drive188of motor80.

Seals192define there between an annular lubricant passage194which is in communication with inlet84. Rotatable portion186includes outer and inner pipes196and198defining there between an annular lubricant passage200. Outer pipe196defines a plurality of radially extending and circumferentially spaced lubricant passages202in fluid communication with annular passages194and200. Thus, passages140of coupling member130are in communication with annular passage200. The configuration of feed swivel82allows for the rotation of portion186while maintaining continuous fluid communication between passages202and annular passage194. A first connecting member130is connected to outer and inner pipes196and198and extends forward therefrom to couple with a second coupling member132in order to provide connection with the remainder of pilot tube48. The arrows inFIGS. 9 and 11indicate the flow of lubricant through the various passages from swivel82through pilot tube48and steering head88.

The operation of boring machine10is now described with reference toFIGS. 12-19.FIGS. 12-16are shown without main frame12of machine10for simplicity.FIG. 12shows assembly42prior to the jacking or driving of pilot tube48to form a pilot hole with an operator204preparing to begin operation of assembly42. The pistons of piston cylinder combinations112are shown in a fully retracted positionFIG. 12. Assembly42is operated to actuate combinations112in order to extend pistons116thereof to drive pilot tube48into ground8as indicated in arrow E inFIG. 13to form the initial stages of a pilot hole206. During the extension of pistons116and pilot tube48, camera100senses or receives input from LED target104and relays the images of illuminations180on the monitor102. Operator204views display monitor102in order to determine whether steering head88needs to be adjusted to maintain the line and grade of pilot tube48. Operator204will use controls108in order to make any necessary adjustments, specifically rotating pilot tube48as indicated in arrow F inFIG. 13via motor80. For use with longer pilot holes, machine10may include additional steering control mechanisms, as described in further detail in the copending application entitled Auger Boring Machine With Two-Stage Guidance Control System which is incorporated herein by referenced and filed concurrently herewith.

Simultaneously with driving and steering pilot tube48and in accordance with invention, water is pumped through pilot tube48via swivel82to steering head88and through the exit openings thereof in order to facilitate the formation of pilot hole206. At this early stage of pilot hole formation, only one of the standard size pilot tubes124A is being used, as shown inFIGS. 12 and 13. Drive mechanism110thus drives pilot tube48for the entire length of tube segment124A or farther, while the frame of assembly42remains stationary and preferably with a single continuous stroke of pistons116. Likewise, roller assemblies68and70travel along surfaces76and78this distance and pistons116extend this distance as well.

Further regarding the operation of the lubrication system of the present invention and with reference toFIG. 14, lubricant typically in the form of water211flows through pilot tube48and steering head88as indicated by the various arrows within the passages previously described. Water211thus flows forward from passages179out of opening90and rearwardly along steering face189. Water also flows through the various passages178and out of opening92to form a rearwardly flowing sheath213of water which surrounds or substantially surrounds the outer surface of pilot tube48. Sheath213of water thus substantially reduces the friction between the outer surfaces of tube48and soil8during the formation of pilot hole206. This reduction in friction thus facilitates the forward movement of pilot tube48and its rotation as indicated at arrow G inFIG. 14. In addition, a layer215of water which forms along steering face189helps reduce the frictional engagement between face189and soil8during the formation of the pilot hole206. Water211will also carry some of soil8entrained therein rearwardly along pilot tube48and into pit6.

Once the initial driving of tube48is performed, pistons112are retracted and a second pilot tube segment124B is positioned and connected to tube segment124A and rotatable portion186of swivel82as indicated at arrow H (FIG. 15) in preparation for additional driving of tube48. Drive mechanism110is then operated to extend piston116, roller assemblies68and70and pilot tube48including segments124A and B to lengthen pilot hole206. Once again, this is achieved in a single continuous stroke as indicated at arrow J inFIG. 16while operator204provides any rotational adjustment to steering head88as indicated at arrow K. Most preferably, the distance that drives mechanism110drives tube48is greater than the length of the pilot tube124B to be inserted in order to make sufficient room for the coupling thereof subsequent to retraction of pistons116. The pattern of adding tube segments and continuing to drive pilot tube48goes on until the pilot hole is completed or more particularly so that the pilot tube48extends out of ground8into a space which may be another pit207where sections of pilot tube48may be removed as the auger boring operation is underway and thus moves pilot tube48gradually forward.

Once pilot hole206is completed, assembly42is removed from frame12of auger boring machine10as indicated at arrow L inFIG. 17. As shown inFIG. 18, auger34is then connected to output shaft32along with the pipe or casing208in which auger34is disposed and cutting head210connected to the front of auger34. A swivel212is also connected to the trailing end of pilot tube48and the front of cutting head210to allow for the rotation of auger34and cutting head210without rotating pilot tube48. Swivel212is described in greater detail in the copending application Method of Installing Large Diameter Casing and Swivel For Use Therewith which is incorporated herein by referenced and filed concurrently herewith. Cutting head210and casing208has a diameter D2which is substantially larger than that of the diameter D1(FIG. 17) of pilot tube48. As shown inFIG. 19, engine24is then operated to rotate output shaft32, auger34and cutting head210(arrow N) as engine24moves forward on rails36with auger34as indicated at arrow P to form a larger diameter hole214in which casing208will be disposed to form underground piping. Auger34carries soil cut by cutting head210rearwardly to discharge from its trailing end so that it can be removed from pit6. Additional casings208with augers34disposed therein are connected in end to end fashion to increase the length of the pipe to be laid, each casing208being welded to the subsequent casing208. It is noted that engine24serves as a single power source for operating auger34as well as for powering the drive mechanism of the pilot tube control and guidance assembly via generator26and hydraulic pump28(FIG. 2), as described in further detail in the copending application entitled Auger Boring Machine With Included Pilot Tube Steering Mechanism which is incorporated herein by referenced and filed concurrently herewith.

Referring toFIGS. 20-22, a second embodiment of a pilot tube segment224is described. Segment224is similar to segment124except for the structures adjacent the ends thereof. Segment224includes a central section226and first and second coupling members228and230connected to opposite ends thereof. Central section226includes a cylindrical outer pipe232and a concentric cylindrical inner pipe234which define therebetween an annular passage236which extends substantially the full length of central section226. Inner pipe234defines a central passage238through which the line of sight Z passes.

First coupling member228includes an annular member240rigidly mounted on outer pipe232. An internally threaded collar242is rotatably mounted on annular member240in a manner similar to that of collar152of coupling member132. Annular member240has a cylindrical outer surface a portion of which is disposed within outer pipe232closely adjacent the inner surface of outer pipe232. A central through passage is formed in annular member240and includes a cylindrical rear passage section244and a hexagonal front passage section246in communication therewith. The leading end of inner pipe234is received within rear passage section244with a pair of annular seals248circumscribing inner pipe234to form a seal with annular member240. Three lubricant passages250are formed in annular member240which are disposed radially outwardly from the central passage thereof and spaced equally circumferentially. Passages250extend from the leading end to the trailing end of annular member240and communicate with annular passage236. Three alignment tubes251are rigidly mounted respectively within passages250adjacent their leading ends and extend forward of the leading end of annular member240.

With reference toFIGS. 20 and 22, second coupling member230includes an annular member252rigidly welded to outer pipe232. Member252has an externally threaded section254adjacent its trailing end for threadably engaging an internally threaded collar242of another pilot tube segment224. An annular seal256circumscribes a portion of annular member252forward of threaded section254for making a seal with collar242of another segment224. A central through passage is formed in annular member252and includes a cylindrical front passage section258and a hexagonal rear passage section260in communication therewith. The trailing end of inner pipe234is received within section258and sealed therewith by a pair of annular seals262. Three lubricant passages264are formed in annular member252radially outwardly of the central passage thereof and are circumferentially spaced equally from one another. Each passage264extends from the leading end to the trailing end of annular member252and communicates with annular passage236.

Referring toFIG. 23, a pipe or connector266includes a hexagonal central section268and first and second cylindrical end sections270and272which are stepped inwardly from and connected to opposed ends of central section268. A pair of annular grooves274is formed in each of sections270and272with respective annular seals276disposed therein.

FIG. 24shows two pilot tube segments224connected to one another. To assemble the two segments224, alignment tubes251are aligned with respective passages264and extend respectively into said passages when the two segments224are joined to one another. Collar242is rotated to threadedly engage threaded section254to draw the two segments224together so that the leading end of annular member240abuts the trailing end of annular member252with the central passages aligned with one another. During the connection, connector266is slidably received within the central passages of annular member240and252. More particularly, first cylindrical end section270is received within a portion of cylindrical front passage section258while a portion of hexagonal central section268is received within hexagonal rear passage section260of annular member252. Seals276provide a seal between end section270and the inner surface of annular member252. In a similar fashion, second end section272is received within cylindrical rear passage section244and a portion of hexagonal central section268is received within hexagonal front passage section246of annular member240. Seals276form a seal between section272and the inner surface of annular member240.

The hexagonal inner surface of central section268is of a mating configuration with the hexagonal inner surfaces of passage sections246and260so that connector266provides a torque drive between annular members240and252and thus between the two pilot tube segments224. Connector266simply slides into the respective central passages of annular member240and252during connection and is slidably removable therefrom during disconnection of segments224. Only the threaded connection between collar242and threaded section254secures the two tube segments224rigidly to one another. As with various other elements of the pilot tubes, a central through passage278is formed in connector266to provide for line of sight Z to extend therethrough. Passage278is thus in communication with the respective passages238of the adjacent pilot tube segments224when connected. Likewise, passages250are in communication respectively with passages264.

FIG. 25shows a second embodiment of a leading pilot tube segment280with an alternate steering head282connected to the leading end thereof. Unlike the earlier embodiment in which lubrication passages are formed in the steering head, steering head282is a standard steering head while pilot tube segment280allows water to flow through the lubrication passages thereof to its outer surface. Segment280includes a central section284which is formed of a single cylindrical side wall as opposed to inner and outer concentric pipes. Connected to the trailing end of central section284is one of coupling members230, which was described earlier with reference to pilot tube segment224. Connected to the leading end of central section284is a steering head coupling member286for coupling with steering head282. Coupling member286utilizes one of internally threaded collars242rotatably mounted on an annular member288which is rigidly connected to a leading end of central section284. A hexagonal through passage290is formed in annular member288and extends from the leading end to the trailing end thereof.

A central through passage292is formed in the side wall of central section284and includes an interior chamber in which one of LED targets104is disposed. Central passage292communicates with hexagonal passage290. A pair of annular seals294provide a seal between target104and the inner surface of the side wall of central section284. An alignment screw296extends through a hole formed in the side wall of central section284and threadedly engages a portion of target104so that it is aligned properly within tube segment280. A pair of check valves298are disposed within passages formed in the side wall of central section284to allow water to be blown out of central passage292if necessary to insure that there is a clear view of target104via line of sight Z, which extends through passage292.

Steering head282includes a solid front body300with a steering face302, an annular member304welded to the trailing end of front body300and a hexagonal drive shaft306which is received within a leading hexagonal cavity308extending forward from the trailing end of annular member304. Annular member304adjacent its trailing end includes an externally threaded section310threadedly engaging collar242. An annular seal312is disposed in a groove forward of threaded section310for making a seal with the leading end of collar242. When steering head282is connected to pilot tube segment280, the trailing portion of hexagonal drive306is received within hexagonal passage290, which is of a mating configuration for providing a torque connection therebetween.

A plurality of lubricant passages314are formed in the side wall of central section284and extend forward from adjacent a trailing end thereof and terminate rearwardly of target104. A plurality of short radially extending passages316extend outwardly from adjacent the trailing ends of passages314and have respective exit openings318on the outer surface of the side wall of central section284. Passages314and316are respectively disposed radially outwardly of central passage292and circumferentially spaced equally from one another. A short inner pipe320extends from within central passage292of central section284into front passage section258of annular member252. Several annular seals322provide for a seal between inner pipe320and each of central section284and annular member252. An annular passage324is formed externally to inner pipe320and internally to a trailing portion of the side wall of central section284and communicates with passages264and314.

Thus, the various passages formed in pilot tube segments224and280allow for water to be pumped therethrough and exit to the outer surface of leading pilot tube segment280adjacent steering head282, as shown by the arrows within the passages. Typically, exit openings318are spaced only a foot or two rearwardly steering head282. Thus, water may flow out of exit openings318forward and rearwardly thereof to provide a sheath of water around the pilot tube which provides lubrication as previously discussed with the earlier embodiment.

Thus, boring machine10provides a pilot tube drive assembly with a lubrication system which feeds lubricant typically in the form of water through the pilot tube and optionally through the steering head in order to facilitate the formation of the pilot hole, thus making the process substantially more efficient.