Combined Bucket Drill and Soil Screen Apparatus and Method for Archaeological Excavations

Abstract

One embodiment of a bucket drill and soil screen apparatus consists of a mast (9) attached to a prime mover vehicle (7). A carriage (10) and hydraulic motor (12) slide vertically along the mast from which an attached kelly bar (14) and drilling bucket (15) are rotated and lowered into the ground. A kickout assembly (13) lifts drilling bucket (15) outward in an arc. Soil and cultural artifacts are transferred to a screen basket (20) by rotating open the drilling bucket through a latch and hinge. The screen basket is lifted to its screening position and rotated around a central axis to facilitate the passing of fine soil particles through the hardware cloth walls of the basket. Cultural artifacts retained in the screen basket are transferred to a fixed sorting screen (22) by rotating the screen basket to its dump position.

Claims

1. A combined bucket drill and soil screen apparatus for excavating archaeological test pits, comprising: a drill mast attached to a prime mover vehicle having a carriage and drive motor slidably attached to said drill mast, and a means for conveying energy from said drill mast to said carriage such that the drive motor can be controllably lifted and lowered; a drilling bucket comprising a cylinder and a floor; and said floor having at least one digging edge and inlet port; and said inlet port having a selectable open position and closed position; and means for coupling rotational energy from said drive motor to said drilling bucket; a soil screen mechanism attached to said drill mast having a drive actuator and a pivotally attached screen basket, wherein the walls of said screen basket having a multitude of openings of predetermined size; and means for coupling rotational energy from said drive actuator to said screen basket thereby causing soil particles to pass through said multitude of openings; means for transferring soil from said drilling bucket to said screen basket; means for transferring cultural artifacts retained within said screen basket to a detached sorting screen; means for controllably coupling power from said prime mover vehicle to said motors and actuators; whereby discrete volumes of soil are captured and extracted from an archaeological test pit at measured excavation depths and the extracted soil is screened to separate and collect cultural artifacts contained within the soil.

2. A method for excavating archaeological test pits and screening the extracted soil for the recovery and collection of cultural artifacts contained within the soil, comprising: providing a drill mast attached to a prime mover vehicle having a carriage and drive motor slidably attached to said drill mast, and a means for conveying energy from said drill mast to said carriage such that the drive motor can be controllably lifted and lowered; providing a drilling bucket comprising a cylinder and a bottom; and said bottom having at least one digging edge and inlet port; and said inlet port having a selectable open position and closed position; and means for coupling rotational energy from said drive motor to said drilling bucket; providing a soil screen mechanism attached to said drill mast having a drive actuator and pivotally attached screen basket, wherein the walls of said screen basket having a multitude of openings of predetermined size; and means for coupling rotational energy from said drive actuator to said screen basket thereby causing soil particles to pass through said multitude of openings; rotating and lowering said drilling bucket into the ground to a measured depth, thereby capturing a discrete volume of soil within said drilling bucket; lifting said drilling bucket and captured soil from the excavated pit to a dump position; opening and emptying said drilling bucket and transferring captured soil to said screen basket; lifting said screen basket to an operating position applying rotational energy to said screen basket thereby causing soil particles to pass through said multitude of openings; transferring cultural artifacts retained in said screen basket to a detached sorting screen; collecting cultural artifacts from said sorting screen; repeating the above steps until the desired excavation depth is obtained within the excavated pit; whereby discrete volumes of soil are systematically removed from the excavation pit at measured excavation depths and the extracted soil is screened to recover and collect cultural artifacts contained within the soil.

Description

DRAWINGSFIGURES

[0042] Included are three drawing sheets containing six figures. Component numbers are consistent across all six figures. Table 1 provides a list of components and associated numbers:

[0043] FIG. 1 is a perspective view showing the configuration of the apparatus during soil excavation.

[0044] FIG. 2. is a perspective view showing the configuration of the apparatus when dumping soil from the drilling bucket.

[0045] FIG. 3. is an elevation view showing the orientation of the screen basket when receiving soil from the drilling bucket.

[0046] FIG. 4. is an elevation view showing the orientation of the screen basket when rotating to remove fine soil particles.

[0047] FIG. 5. is an elevation view showing the orientation of the screen basket when transferring cultural artifacts into an unattached sorting screen.

[0048] FIG. 6. Is a perspective view detailing the kelly bar and slip clamp.

DRAWINGS-LIST OF REFERENCE NUMERALS

[0049] 7 Prime mover vehicle with auxiliary hydraulic circuit [0050] 8 Quick connector plate assembly [0051] 9 Drill mast [0052] 10 Carriage for drive motor [0053] 11 Hydraulic control valve [0054] 12 Drive motor [0055] 13 Drilling bucket kickout assembly [0056] 13a Kickout actuator [0057] 13b Kickout lever [0058] 14 Telescoping kelly bar assembly [0059] 14a Inner kelly bar shaft [0060] 14b Outer kelly bar tube [0061] 14c Linchpin [0062] 14d Slip retaining tabs [0063] 15 Drilling bucket [0064] 16 Lift arm spindle and hydraulic actuator [0065] 17 Lift arm [0066] 18 Screen basket spindle [0067] 19 Hydraulic motor for rotary screen basket [0068] 20 Screen basket [0069] 21 Handles for tipping the screen basket [0070] 22 Detached free-standing sorting screen [0071] 23 Kelly bar slip clamp [0072] 24 Excavated test pit

DETAILED DESCRIPTIONFIRST EMBODIMENTFIGS. 1-6

[0073] A skid steer track loader 7 with an auxiliary hydraulic circuit is used as a prime mover vehicle to move the apparatus between test pit locations and to power the hydraulic motors and actuators (FIG. 1). The apparatus consists of a drill mast 9 that is attached to track loader 7 through a quick connector plate assembly 8. This plate assembly 8 is fastened to the drill mast with fourteen bolts and can be adjusted up or down to accommodate differing heights in prime mover vehicles. A four-spool hydraulic control valve 11 is mounted to the right side of the drill mast 9. Hydraulic hoses with quick connectors supply hydraulic flow to the control valve 11 from the auxiliary hydraulic ports of the track loader 7.

[0074] A hydraulic motor 12 is mounted onto a carriage 10 with two pintles that allow the motor 12 to pivot within the carriage 10. A kickout mechanism consists of a hydraulic actuator 13a that connects to a lever 13b. The upper end of the lever 13b connects to the pintle of the drive motor 12 and the lower end of the lever 13b presses against the drive motor in a manner that permits the hydraulic actuator 13a to push or pivot the lower portion of the drive motor outward away from the drill mast 9. The carriage 10 is designed to slide up and down along the vertical extent of the drill mast 9. The carriage is suspended by a hoist mechanism that consists of roller chains and idler sprockets configured as a bi-directional gun tackle. The roller chains connect to the end of a hydraulic actuator mounted to the backside of the drill mast 9. Extension and contraction of the hydraulic actuator causes the carriage 10 to slide along the drill mast 9 a distance equal to twice the stroke length of the hydraulic actuator.

[0075] A square telescoping kelly bar assemblage 14 connects to the shaft of the drive motor 12 (FIGS. 2 and 6). The kelly bar assemblage 14 includes a solid inner kelly bar shaft 14a that slides into an outer kelly bar tube 14b. Welded to the end of the inner bar 14a is a hub that permits quick attachment to the hydraulic motor 12 with a linchpin. A linchpin 14c locks the position of the inner shaft 14a relative to the outer tube 14b. Two sets of linchpin holes in the inner shaft 14a allow the kelly bar assemblage 14 to be configured in a collapsed position or an extended position. Two flanges 14d welded to the outer tube 14b provide a footing for a kelly bar slip clamp 23. The slip clamp 23 slides around the kelly bar and under the flanges 14d. The slip clamp straddles the excavated hole to prevent the outer tube 14b from falling deeper into the hole when the linchpin 14c is removed. The bottom of the outer kelly bar tube 14b connects to a drilling bucket 15 with a linchpin.

[0076] The lid plate of the drilling bucket 15 connects to cylindrical walls of the drilling bucket through a hinge mechanism and a spring-loaded latch mechanism, each located at opposing positions along the upper rim of the bucket (FIG. 2). A manually triggered trip arm releases the spring-loaded latch mechanism allowing the bucket to open along a hinge at the top of the drilling bucket 15. The drilling bucket 15 has two bottom plates, one that is firmly attached to the circumference of the drilling bucket and the other that rests flush against the bottom of the fixed plate, but freely rotates approximately 90-degrees along a central spindle. Both plates have two matching openings or inlet ports that align when the drilling bucket 15 is rotated in a clockwise direction and closed when rotated in a counterclockwise direction. Two digging edges made from wear resistant steel are welded to the bottom plate along each opening. The digging edges project downward from the plate and are angled in a manner to direct soil upward through the inlet ports when the drilling bucket 15 is rotated in a clockwise direction.

[0077] A lift arm 17 connects to the drill mast 9 through a spindle 16 that is attached to a fixed arm that extends outward from the drill mast 9. A hydraulic actuator causes the lift arm 17 to rotate on the spindle 16 along an arc of approximately 90-degrees. A screen basket 20 connects to the lift arm 17 through a spindle 18. Two adjustable stops along the radius of the spindle 18 set the rotation limits. A hydraulic motor 19 mounts to the screen basket drive assembly. A roller chain contained within the rectangular drive assembly housing transmits power from the hydraulic motor 19 to the center axle of the screen basket 20. Two fixed handles 21 extend outward from the drive assembly. The handles 21 provide manual control over the drive assembly's rotation around the spindle 18.

[0078] The screen basket 20 rotates under hydraulic power along a central axle that is held in place by roller bearings located inside the drive assembly. The screen basket 20 connects to a four-bolt hub at the end of the axle. The screen basket 20 is constructed around a central hub from which radial ribs are welded and extend outward to the bottom ring of the basket. Corresponding vertical ribs are welded to the bottom ring and extend perpendicular to the upper ring of the basket. The rib and ring structure support four-holes-per-inch wire hardware cloth which form the bottom surface and the surface around the circumference of the basket. The upper or outward end of the screen basket 20 is open.

[0079] The hydraulic actuator connected to spindle 16 causes the lift arm 17 to rotate in an arc. When rotated to the bottom or low point of the arc, the screen basket 20 is positioned under the drilling bucket 15 when the drilling bucket is placed in its kicked-out position (FIG. 2). This vertical alignment permits the downward flow of soil from the open drilling bucket 15 to the screen basket 20 (FIG. 3). When the lift arm 17 is rotated upward and outward, the screen basket 20 rests at an angle that best facilitates the movement of fine soil particles through the hardware cloth as the screen basket revolves (FIG. 4). FIG. 5 shows the final position of the screen basket 20 after rotating or tipping the basket along the spindle 18. In this position, cultural artifacts and soil particles too big to pass through the hardware cloth fall from the screen basket 20 and into a detached free-standing sorting screen 22.

OperationFirst Embodiment

[0080] The bucket drill and soil screen method and apparatus achieve their result as follows. The track loader 7 is positioned to engage and attach to the drill mast 9 through the quick attachment plate 8 (FIG. 1). Hydraulic hoses connect the hydraulic control valve 11 to the auxiliary hydraulic ports on the track loader 7. The track loader 7 and attached apparatus are moved to the archaeological test hole location. The drill mast 9 is lowered to rest firmly on the ground surface and the track loader 7 is adjusted so that the mast is perpendicular to the ground surface. The carriage 10 is lowered until the drilling bucket 15 rests on the ground surface.

[0081] To begin excavation, the hydraulic motor 12 is engaged and rotated in a clockwise direction while the carriage 10 is slowly lowered. The rotating drilling bucket 15 cuts into the ground surface as soil is lifted into the drilling bucket by the digging edge. A graduated scale painted onto the front surface of the drill mast 9 serves as a depth gauge as the carriage 10 and drilling bucket are lowered. When the desired depth is reached, the hydraulic motor 12 is stopped and then briefly re-engaged in a counterclockwise direction. The counter rotation closes the bottom plate, thus trapping the excavated soil within the bucket. Carriage 10 is raised to its highest position which lifts the drilling bucket 15 out of the excavated hole.

[0082] Transfer of the excavated soil from the drilling bucket 15 to the screen basket 20 begins with engaging the lift arm spindle and actuator 16 so that the lift arm 17 and screen basket 20 move downward in an arc to their lowest position (FIGS. 2 and 3). Engaging the kickout actuator 13 rotates the hydraulic motor 12 around its pintles, thus lifting the kelly bar 14, and drilling bucket 15 outward and up along an arc to a position overlying the screen basket 20. A trip arm on the lid of the drilling bucket 20 is triggered to release the spring-loaded latch. The drilling bucket 15 is manually lifted on its hinge to a position where its contents fall out of the bucket and into the screen basket 20. When emptied, the drilling bucket 15 is rotated on its hinge until the spring-loaded latch secures the bucket in its closed position. The drilling bucket kickout actuator 13 is engaged and the hydraulic motor 12, kelly bar 14, and drilling bucket 15 return to their vertical drilling position.

[0083] The lift arm actuator at spindle 16 is engaged to elevate the lift arm 17 and screen basket 20 to its working position (FIG. 4). The hydraulic motor 19 is engaged and the screen basket 20 begins to rotate. The rotation of the screen basket 20 causes fine soil particles within the screen basket to fall through the hardware cloth. When the fine soil has dissipated from the screen basket 20, the two handles 21 attached to the drive assembly are used to manually rotate the screen basket 20 counterclockwise around the spindle 18, thus tipping the screen basket 20 toward the detached free-standing sorting screen 22 (FIG. 5). The contents of the screen basket 20 fall into the sorting screen 22. When the screen basket 20 is empty, it is returned to its working position and the hydraulic motor 19 is disengaged to stop the screen basket's rotation.

[0084] Artifacts retained on the sorting screen 22 are collected and placed in a bag with a tag that designates the test hole, excavation level, and depth from which the artifacts were extracted. Any material remaining on the sorting screen 22 is discarded. While the soil and artifacts are being screened and sorted, the drilling bucket 15 is lowered back into the test pit and soil from the next excavation level is captured and lifted out of the hole. This process is repeated until the desired excavation depth is attained within the test pit. The track loader and apparatus are then moved to the next test pit location. Completed test pits are backfilled manually with spade shovels or at the end of the day using the track loader with a standard dirt bucket attachment.

[0085] If the archaeological deposits within a test hole extend to a depth below the reach of the collapsed kelly bar assembly 14, then the kelly bar is extended to increase its vertical reach. This requires the additional steps of extending the kelly bar 14, capturing the soil in the next excavation level, and then collapsing the kelly bar 14 so that the drilling bucket 15 can be removed from the hole. The inner kelly bar 14a is extended by removing the linchpin 14c, lifting carriage 10 to the top of the drill mast 9, and re-installing the lynch pin 14c to lock the kelly bar 14 in its extended configuration. This process is reversed to collapse the kelly bar 14. A kelly bar slip clamp 23 is placed around the kelly bar 14 before the linchpin 14c is removed which prevents the outer kelly bar tube 14b and drilling bucket 15 from falling deeper into the test pit. To further increase the excavation depth, additional kelly bar extensions can be inserted between the expanded kelly bar assembly 14 and the hydraulic motor 12 as needed. This first embodiment can extract soil from depths up to 3 meters. Additional kelly bar extensions can be added to increase excavation depth to greater than 3 meters.

Conclusion, Ramifications, and Scope

[0086] At least one embodiment of the combined bucket drill and soil screen provides an alternative method to the manual excavation of archaeological test pits while reducing costs in time and labor and improving worker safety. The above described embodiment reduces the problem of soil mixing between excavation layers, thus improving the separation and recovery of cultural artifacts from discrete excavation levels. My above description of a combined bucket drill and soil screen contains many specificities; however, these specificities should not be construed as limitations, but rather as an example of one embodiment. Many variants are possible.

[0087] There are several alternative embodiments in which the combined bucket drill and soil screen method can achieve the same results. [0088] Alternatives to the skid steer track loader 7 power unit, include wheeled skid loaders, walk-behind skid loaders, stand-behind skid loaders, farm tractors, track loaders, wheeled loaders, remote controlled crawler tractors, hydraulic excavators, truck chassis, and trailer chassis. [0089] The height of the drill mast and length of the kelly bar 14 can be varied for differing excavation depths and track loader 7 carrying capacities. [0090] Alternatives for the hydraulic cylinder and roller chain gun tackle that actuate the vertical movement of the carriage 10 include a hydraulic cylinder and a wire rope gun tackle assembly or a configuration in which the carriage 10 and attached roller chain is actuated by a combination of sprockets and gears driven by a hydraulic motor. [0091] The diameter and length of the drilling bucket 15 can be varied to accommodate test pit size requirements. [0092] A drilling bucket 15 with a fixed lid plate and hinged bottom plate can be used to empty the drilling bucket through the bottom. [0093] Alternatives to the bucket kickout mechanism 13 include various configurations of hydraulic cylinders and levers that push or pull the hydraulic motor and kelly bar outward to the drilling bucket dump position. [0094] An alternative to the drilling bucket kickout mechanism 13 includes a mechanical kickout bar used to force the kelly bar and drilling bucket 15 to arc outward to its dump position when the carriage 10 is lowered. One end of the kickout bar connects to the top of the kelly bar 14 in a manner that allows the bar to pivot outward. The other end of the kickout bar inserts into a slot on the drill mast 9. Lowering the carriage 10 causes a downward force on the kickout bar. The geometry of the kickout bar relative to the drill mast 9 is configured so that the downward force is relieved by propelling the hydraulic motor 12 and kelly bar 14 outwards. [0095] Differing lift arm 17 lengths, geometries, and actuator mechanisms can be used to move the screen basket 20 to its various working positions. In one variation the screen basket lift arm remains fixed at the spindle 16 and a washtub is place under the drilling bucket 15 when in its kickout position. Soil from the drilling bucket 15 is dumped into a wash tub. The washtub is then manually lifted over the opening in the screen basket 20 and the soil is emptied into the basket. [0096] The diameter and depth of the screen basket 20 and the opening size of the hardware cloth can be varied to accommodate differing soil conditions and artifact collection policies. [0097] Alternative screening systems can be used including varying geometries of rotating baskets, trommel screens, and flat screens that shake, oscillate, vibrate, or any combination of these movements. [0098] Various tools mounted within the screen basket 20 may be designed to assist in breaking up soil clods and to force fine soil particles through the hardware cloth, including flights or baffles made of various materials that redistribute soil within the basket; rubber pads or flaps that push soil against the hardware cloth; or assemblies of shaft mounted rubber-fingered rollers and stars that rotate against the inner surfaces of the hardware cloth. [0099] Instead of emptying the screen basket 20 directly into the free-standing sorting screen 22 (FIG. 5), a sheet metal baffle may be placed under the screen basket in a position that directs the coarse soil particles and artifacts into a bucket or tub. The bucket or tub is then manually lifted and emptied into the sorting screen located near the apparatus.