GB2138473A - Utility line excavation - Google Patents

Abstract

A method of excavating a buried utility line for repair, maintenance or the like includes the steps of commencing an excavation above the location of the buried utility line, inserting into the excavation a tool with a head portion (20) that carries an array of spring fingers and a drive (24) for the spring fingers, energizing the drive while positioning the head portion adjacent compacted soil in the excavation to drive the array of spring fingers, deepening the excavation by manipulating the tool head in the excavation to cause the array of the spring fingers to loosen soil in the excavation, and removing the loosened soil from the excavation to expose the buried utility line. Particular apparatus employs an electrically isolated fluid drive which minimizes risk of shock to the operator or damage to buried utility lines and efficiently loosens soil around and beneath buried utility lines. <IMAGE>

Description

SPECIFICATION Utility line excavation This invention relates to soil excavation, and more particularly to methods and apparatus for excavation underground utility line installations such as gas distribution pipelines for repair, maintenance and the like.

Accidental damageto underground gas distribution pipelinesthatoccurs during excavation for repair, maintenance orthe like is a significant and costly problem forthe natural gas industry. Present utility line excavation methods rely largely on heavy equipment such as backhoes trenchers, jackhammers and bulldozers which maydamagethe utility line, creating hazardous conditions, service interruptions and additional operating expenses to repairthe damaged pipe and to restore service. Excavation systems that employ a vehicle with an air lineto loosen the soil and a vacuum transport system to remove the soil from the excavation have also been used at times.In instances where space constraints, as in many urban locations, prevent use of heavy excavation equip ment,thehand digging required is costlyand time consuming.

In accordance with one aspect ofthe invention, a method of excavating a buried utility line for repair, maintenance orthe like includes the steps of commencing a excavation above the location ofthe buried utility line, inserting into the excavation a tool with a head portion that carries an array of spring fingers and a driveforthe spring fingers, energizing the drive while positioning the head portion adjacent compacted soil in the excavation to drive the array of spring fingers, deepening the excavation by manipulating the tool head in the excavation to cause the array of the spring fingers to loosen soil in the excavation, and removing the loosened soil from the excavation to expose the buried utility line.Preferablu,the array of spring fingers is driven in rotation while the tool is in the excavation to provide a spring finger tip velocity of at least on hundred meters per minute.

The loosened soil may be removed from the excavation concurrently with the loosening action as by means of a vacuum line.

In accordance with another aspect of the invention, there is provided a hand manipulated soil dislodging tool for use in excavating buried utility lines. Atool head, supported in cantileverfashion atthe end of an elongated manipulating support pole, includes an array of generally radially extending flexibletine members. Atool head drive motor is also disposed at that end of the pole for driving the tine members, and a control adjacentthe opposite end ofthe elongated manipulating pole controls operation ofthe drive motor.Insertion of the hand manipulated tool into an excavation and energization of the motor drives the tine members in effective dislodgement action of difficult to excavate soils such as compacted and frozen soils and heavywetclaysoilssuchthatthe dislodged soil material may be removed from the excavation by suitable means such as a vacuum system. The cantilevered array of flexible tines impact the compacted soil in the excavation with a repetitive and controlled resilientflexing action that rapidly loosens soil for removal from the excavation without harm to buried utility lines such as plastic or metal pipe, electric cable, television cable and the like.An angularly offset cantilevered head configuration facilities excavation along side and underneath a buried utility line, efficiently provides access to buried utility lines without requiring large excavations or use of heavy equipment, and may be used to clean surfaces of exposed gas distribution pipelines in preparation for modification, repair or the like.

In a particular embodiment, six rows of dislodgment tinesintheform of spring fingers extend in circumferential arrayofalong an axial length of about eleven centimeters ofthe soil dislodgement head with fifteen spring fingers in each row. Each spring finger has a soil dislodgement portion that extends a radial distance of about six centimeters from a cylindrical support and an integral restraining portion that is seated against the central drive shaft ofthe dislodgement head.Whilevarious spring finger matrials (including non-metallic materials) may be used depending on particular soil applications, the spring fingers in this embodiment are of two millimeter diameter carbon steel spring wire (music wire) and have a Rockwell Chardnessofabout45,atorsion elastic limit of about 100,000 psi and a tensile strength of at least about 250,000 psi. These spring fingers are mounted on support rods that are circumferentially disposed about the axis ofthe dislodgement head and the support rods are in turn supported bydiscsthat are coupled to the central drive shaft.The drive, a hydraulic motor attached at the end of a six-foot long electrically insulating tubular pole that houses electrically insulating hydraulicfluid supply and return lines, rotates the dislodgement head at controllable speeds of up to 2,500 rpm, producing tine tip velocities of up to about 1,500 meters per minute. As the tips ofthe flexible spring fingers strike the soil they provide relatively gentle and effective flicking and soil dis lodgement action that quickly loosensthe soil for removal from the excavation. Avariety of specific dislodgement actions can be achieved depending on factors such asthe velocity ofthetinetips andthe force applied to the tool head via the manipulating pole.As soil dislodgement resistance is encountered, the restraining portions ofthe spring fingers tend to seat on the drive shaft such thatthe flexing and dislodgement action of the tool is enhanced. The modular arrangement of spring finger units facilitates adjustmentofthe axial length ofthetool head depending on the particular utility line excavation application.

The invention provides a lightweight, compact and versatile hand manipulated excavation tool that effectively excavates a variety of soil types and conditions -- backfilled, load bearing, frozen, etc; thatis easily manipulated in confined spaces and minimizes the size of the excavation required; that efficiently loosens soil around and beneath buried utility lines; and that employes an electrically isolated fluid drive which minimizes risk of shockto the operatoror damageto buried utility lines.

Otherfeatures and advantages ofthe invention will be seen asthefollowing description of a particular embodimentprogesses, in conjunction with the drawings, in which: Fig. is a diagrammaticview of utility line excava tion in accordance with the invention; FIG. 2 is a perspective view ofthe excavation tool employed in Fig. 1; Fig. 3 is an end view, with parts broken away, of the excavation head ofthetool shown in Fig. 2; Fig. 4 is a sectional view ofthe excavation head taken along the line4-4of Fig. 3; Fig. 5 is a side view of an excavatortine employed in the head shown in Fig. 3; and Fig. 6 is an end view ofthe excavatortine shown in Fig.5.

With reference to Fig. 1, buried gas distribution pipe 10 isatthebottom of partial excavation 12. A hole 14 has been formed in pavement 16 by conventional means to commence the required excavation to expose utility line 10. Further excavation to expose distribution line 10 is performed by portable, hand manipulated excavation tool 18 that includes a cantilevered excavation head 20 atthe lower end of six foot long tubularfiberglass support pole 22. Hydraulic motor24atthe end pole22 is coupled in driving relation to excavation head 20 and is supplied with hydraulic fluid through supply and return lines 26 from hydraulic power unit28.Power unit28 supplies hydraulicfluid ata rate of approximately 2112 gallons per minute and a pressure of 1500 psi. Control handle 30 atthe upper end of pole 22 controlstheflow of hydraulicfluidto hydraulic motor 24.

Further details of excavating tool 18 may be seen reference to Figs. 2-4. Hydraulicfluid is supplied to drive motor24through hydraulic lines 26 that pass through manipulating pole 22. Control handle30 includes deadman lever42 which operates control valve 44to control flow of hydraulic fluid from power unit 28to drive motor 24. Dislodgement head 20 includes drive shaft 34 on which a series ofthree spaced drive discs 36 are mounted. Each disc is of twenty gauge steel and has a diameter of about eight centimeters.Extending through and secured to the series of support discs 36 in circumferential array about driveshaft 34 are a series of six support assemblies 38, each of which carries a series offifteen excavatortines 40. Deflectorshield 45 is secured to pole 22 by coupling 47.

Further details of the modular soil dislodgement head 20 may be seen with reference to Figs. 3 and 4.

Drive shaft 34 is of hexagonal configuration and about eleven centimeters in length, is attached to shaft 46 of hydraulic motor 24 by a threaded coupling 48 and has securing cap 50 at its opposite end. Each tine support assembly 38 include shaft 52 that carries a series of cylindrical spacertubes 54 that spacethe discs 36.

Each spacertube 54 has a length of about 3.5 centimeters and a diameter of about 1.3 centimeters, and each support 52 has internally threaded ends that receive fastener bolts 56.

Mounted on each support assembly 38 are a series offifteen excavatortines40 oftwomillimeterdia- meter carbon steel spring wire (music wire), each tine having a disiodgementportion EOaboutseven centi- meters in length, a cylindrical support portion 62 that is composed ofthreeturns ofwire and has a diameter of about 1.7 centimeters and a restraining portion 64 that is about3.2 centimeters in length and offsetfrom tine portion 60 by an angle of approximately 105% The support portions 62 offices 40, as indicated in Figs. 3 and 4, are received on spacertubes 54in groups of five between discs 36such that restraining portions 64 seat against a flat ofthe hexagonal drive shaft 34 and dislodgement portions 60 extend radially ata rake angle of about from the supporttubes 38 such that the dislodgementtips 66 define a circle that is about nineteen centimeters in diameter. The excavator head is of modularconstruction,facilitating change or replacement of individual tines, and its length can be adjusted by adding or subtracting one or more discs and sets ofexcavatortines as appropriatefor a particularapplication.

In use, hydraulic power unit28 is energized to flow hydraulic fluid to tool 18. Excavation head 20 is inserted into the preliminary excavation 12,asindi- cated in Fig. 1, and when control 30 is operated, hydraulic fluid flows to motor 24 and drives soil dislodgement head 20 in rotation. The seiected rotational speed of head 20 depends on the soil conditions encountered-a 200 rpm speed being suitable for dry sand whilefull rotational speed being usedfor difficult soil conditions such as blue clay.The operator positionsthe dislodgementhead 20 adjacent a wall ofthe excavaton so thatrehe excavator tines 40 impact with resilientflexing action on and loosen the soil 70, the loosened soil being removed from the excavation l2bysupplemental means such asa vacuum system diagrammatically indicated at72. The soil loosening action of the multiple flexible tines is readily adjusted by changing tip velocity andlor pressure againstthewall ofthe excavation as a function ofthe type of soil being excavated.The depth ofthe excavation is increased rapidly and efficiently with minimal possibility or accident or damageto pipe 10 orto other adjacent utilitylines.Afterthe gas distribution pipe 10 has been exposed, the cantilevered head 20 may be manipulated around and beneath the exposed pipeforfurther exposure andlor cleaning to facilitate the necessary repair or maintenance.

Buried utility lines such as gas distribution pipes are rapidly and effectively exposed in a wide variety of soils, including wet clay soils, and a variety of soil conditions, including frozen soils. The excavation action ofthe multipleflexibletines is controlled by varyingtheflowof hydrauliefluidto drive motor24via the hand operated deadman valve control 42 and the electrically isolating pole and hydraulic lines.

While a particular embodiment ofthe invention has been shown and described, various modifications thereofwill be apparenttothose skilled in the art and therefor it is not intended thatthe invention be limited to the disclosed embodiment orto details thereof and departures may be made therefrom within the spirit and scope ofthe invention.

Claims (22)

1. A method ofexcavating a buried utility line for repair, maintenance orthe like comprising the steps of commencing an excavation above the location of the buried utility line, inserting into said excavation a tool with a head portion that carries an array of spring fingers and a drive for said spring fingers, energizing said drive while positioning said head portion adjacent compacted soil in said excavation to drive said array of spring fingers, deepening said excavation by manipulating said tool head in said excavation to cause said array of said spring fingers to loosen soil in said excavation, and removing said loosening soil from said excavation to expose the buried utility line.

2. A buried utility line excavation method as claimed in claim 1, wherein said spring fingers are arranged in a circumferential array on said head and said drive rotates said head, said drive being energized to provide a spring fingertip velocity of at least one hundred meters per minute to loosen soil in said excavation.

3. A buried utility line excavation method as claimed in claim 1 or claim 2, wherein said head is angularly offset from the axis of an elongated manipulating support pole, and further including the step of disposing said angularly offset head beneath said buried utility line to loosen soil beneath said line.

4. A buried utility line excavation method as claimed in any one ofthe preceding claims, wherein said soil loosening and removing steps are performed concurrently.

5. A soil dislodging tool for use in excavating buried utility lines that includes an arrayofflexiblespringfingersthataremounted on and extend generally radially from a head that is supported in cantileverdfashion atthe end of an elongated head supporting and manipulating pole, a drive at said end ofsaid pole and coupled to the spring finger head for rotating said head, and a control adjacent the opposite end of said elongated manipulating poleforcontrolling operation of said drive.

6. Asoil dislodging tool as claimed in claim 5, wherein said drive is a fluid motor and further including fluid supply line means carried by said pole and extending between said control and said motor.

7. Asoil dislodging tool as claimed in claim 6, wherein the motor is a hydraulic motor and said fluid supply line means includes hydraulicfluid supply and return lines of electrically insulating material.

8. Asoil dislodging tool of claim 6 or claim 7, wherein said pole is of tubular configuration and said fluid supply line means are housed within said pole.

9. Asoil dislodging tool as claimed in any one of claims 5to 8, wherein said pole is of electrically insulating material and has a length to diameter ratio of at leastabouttwenty.

10. A soil dislodging tool as claimed in any one of claims 5to 9, wherein said head includes a cylindrical array of axially extending support shafts, and each said spring finger is a wire memberthat has a soil dislodgement portion, a body portion and a restraining portion, said body portion being formed by a plurality ofturns of said wire member and being received on a supportshaft such that said dislodge ment portion extends generally radially outwardly from said support shaft and said restraining portion tends to prevent rotation of said body portion on its support shaft.

11. Asoil dislodging tool as claimed in claim 10, wherein each said wire member is of spring metal and has a Rockweli C hardness of at least about40, and a torsion elastic limit of at least about 80,000 psi.

12. A soil dislodging tool as claimed in any one of claims 5to 11, wherein said head includes a drive shaft, a series of radially extending support members spaced axially along said drive shaft, a circumferential array of spring finger supports secured to said support members, said spring fingers being secured to and extending generally radially outwardlyfrom said supports.

13. Asoil dislodging tool as claimed in Claim 12, wherein each spring finger support is an axially extending shaft, and each said spring finger is a wire member that has a soil dislodgement portion, a body portion and a restraining portion, said body portion being formed by a plurality ofturns of said wire memberandbeing receivedonasupportshaftsuch that said dislodgement portion extends generally radially outwardlyfrom said support shaft and said restraining portion tends to prevent rotation of said body portion on its support shaft.

14. A soil dislodging tool as claimed in claim 13, wherein each said wire member is of spring metal and has a Rockwell C hardness of at least about 40. and a torsion elastic limit of at least about 80,000 psi.

15. A soil dislodging tool as claimed in any one of claims 12 to 14, wherein said drive is a hydraulic motor and further including hydraulic fluid supply and return lines carried by said pole and extending between said control and said motor.

16. A soil dislodging tool as claimed in claim 15, wherein said pole is a tubular member of electrically insulating material and has a length to diameter ratio of at least twenty, and said supply and return lines are of electrically insulating material and are housed within said tubular member.

17. Asoil dislodging tool as claimed in claim 16, wherein said control includes a handle portion, a control valve adjacent said handle, and a deadman leverfor operating said valve,

18. A soil dislodging tool as claimed in claim 17, wherein said control valve is adapted to provide a range of hydraulic flow rates to said hydraulic motor so thatthetip velocities of said spring fingers may be varied over a range of at least one hundred-one thousand meters per minute.

19. A soil dislodging tool as claimed in claim 18, wherein said head extends generally at right angles from the axis of said pole and is in axial alignment with said hydraulic motor.

20. A method as claimed in claim 1, wherein said spring fingers and a driveforsaid spring fingers are mounted on and extend generally radially from a head that is supported in cantilevered fashion at the end of an elongated head supporting and manipulating pole of electrically insulating material that has a length to diameter ratio of at least abouttwenty, said drive includes a hydraulic motor at said end of said pole and coupled to said spring finger head for rotating said head, a control adjacent the opposite end of said elongated manipulating pole for controlling operation of said drive, hydraulicfluid supply and return lines of electrically insulating material that are carried by said pole extend between said control and said motor, andfurtherincluding the step of energizing said hydraulic motor drive while positioning said head adjacent compacted soil in said excavation to drive said array of spring fingers.

21. A method of excavating a buried utility line for repair, maintenance orthe like substantially as hereinbefore described.

22. A soil dislodging tool for use in excavating buried utility lines substantially as hereinbefore described with reference to and as shown in the accompanying drawings.