Abstract:
A driver tool provides an apparatus and method for installing shaft objects such as casing, pipes, poles, bars, rods, piles or tubes into the ground or other surrounding media. The driver tool has a steel tower on which is mounted a pneumatic or hydraulic hammer. The hammer is attached to a chain-driven mounting plate controlled by a hydraulic or air-driven motor so that the hammer slides in either direction along the tower. In a typical operating position, the tower is generally vertical to the ground and positioned over a shaft section so that the hammer can drive the shaft object into the ground at a manually controlled rate. The hammer and tower are mounted on a chassis having turf tires for rough terrain capability. In its transport position, the tool is positioned on its tires, with the tower generally horizontal to the ground. As a result, the driver tool can be easily moved and operated by one or two men and operated in limited access areas.

Description:
This application claims the benefit of provisional patent application No. 60/157,970 entitled Portable Injection-Casing Driver, filed Oct. 6, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     Geological grouting is a versatile construction technique used in a variety of applications. Injection casing or piping is driven into the ground. Grout is then pumped under pressure through the above-ground end of the installed casing, out the underground end, and into the surrounding soil. The grout itself can be made from many different materials proportioned in a wide range of amounts depending on the specific grouting application. Cementitious grout, for example, is a mixture of hydraulic cement and water, with or without aggregates and with or without admixtures. Hydraulic cements react with water to form a hardened paste that maintains its strength and durability in water and also maintains its properties upon drying. 
     Grouting applications include slabjacking, mud jacking, subsealing and soil grouting. In slabjacking, pressure grouting is used to raise a depressed section of pavement or other concrete element by forcing a flowable grout under it. Subsealing is where a cement-grout mixture is pumped under pressure through a packer installed in an access hole drilled in a slab to fill voids and depressions under the slab and reduce damage caused by excessive pavement deflections. For soil densification, soil is grouted to increase its bearing capacity, provide radial densification, reduce or halt settlement, increase shear resistance to stabilize it against lateral movement, reduce waterflow, or increase the cohesive strength of friable ground prior to excavation. Soil grouting includes permeation grouting, where a thin grout is used to permeate the soil and fill pores and voids between soil particles; deep-soil mixing, where soil and injected grout are mixed together to make a soil-cement material in place; jet grouting, where a cement-and-water grout is injected under very high pressure to form a concrete-like column; and compaction grouting, described below. 
     Compaction grouting is a soil stabilization process where weak or compromised sub-soils are densified. This technique involves driving injection casing into the soil in five to eight foot sections until good refusal is achieved, usually when the casing reaches bedrock or bearing strata. Pressure grouting is then performed in vertical stages throughout the length of the casing hole. The vertical stages are created by extracting a section of casing a fixed length, typically one to three feet, and then pumping a quantity of stiff, sand-and-cement grout through the casings. An operator monitors an external pump stroke counter at the pump and a pressure gauge at a pump head attached to the casing end. The operator also records the pressures achieved and the quantity of grout injected at each stage. A fully extracted section of casing is removed between stages, the pump head is reattached, and the extraction and grouting sequence is repeated. The stiff grout does not permeate the soil but maintains a grouted mass, three feet or more in diameter. By displacing the soil and forming a bulblike or coluninlike form, the grout significantly increases the soil density at a radial distance of one to six feet or more from the soil-grout interface. 
     SUMMARY OF THE INVENTION 
     Typically, injection casings for compaction grouting applications are installed with a handheld pneumatic or hydraulic hammer. One end of a casing section is attached to the end of a previously installed casing section. A crewman then stands atop a platform, positions the hammer to the unattached end of the casing, activates the hammer and drives the entire casing assembly into the ground. These steps are repeated multiple times. 
     Such handheld hammering methods, however, are potentially hazardous, awkward and time consuming. The pneumatic and hydraulic hammers are heavy and difficult to lift and position on the unattached casing end, which may extend five feet or more above ground-level. The crewman holding the heavy hammer is always at risk of falling off of the platform. This operation requires a two-man crew, with one man repeatedly climbing onto and off-of the platform and the other man transferring the hammer to and from the man on the platform and assisting in assembling the casing sections. 
     One aspect of the portable injection-casing driver according to the present invention is a driver tool for hammering a shaft into a surrounding media comprising a base plate and a tower attached to and extending generally perpendicularly from the base plate. The tower has a first end away from the base plate and a second end near the base plate. A powered hammer is movable along the tower between the first and second ends so that the shaft can be positioned between the media and the hammer when the hammer is near the first end of the tower and so that the shaft can be driven by the hammer into the media as the hammer is actuated and moved toward the second end. 
     The driver tool may also comprise a motor and a mount retained by the tower so as to be movable along the tower. The hammer is attached to the mount and a link is installed between the tower first and second ends. The link is utilized to transfer mechanical energy from the motor to the mount so as to move the hammer. The link may comprise an upper sprocket near the first end, a lower sprocket near the second end, a reduction gear and a drive chain engaging the sprockets and the gear. The motor also engages the gear. In one embodiment, at least one of the sprockets has a spring-loaded tension adjuster configured to dampen mechanical force generated during operation of the hammer. In another embodiment, the reduction gear has a gear ratio in the range of 50:1 to 70:1. In a further embodiment, the base plate has an open-faced slot configured to accommodate the shaft and balance and stabilize the tool. In another embodiment, the tower has a height in the range of 94 inches to 116 inches. 
     In yet another embodiment, the driver tool further comprises a control assembly having a first portion to direct power to the motor in order to raise and lower the hammer, and a second portion to direct power to the hammer in order to actuate and de-actuate the hammer. The first portion and the second portion are independently operable and configured to allow an operator to simultaneously lower and actuate the hammer with one hand. The motor and the hammer may be powered by compressed air. In this embodiment, the first portion comprises a dual-port valve controlled by a first handle to direct compressed air through the motor. The second portion comprises a single-port value controlled by a second handle to direct compressed air to the hammer. 
     In still another embodiment, the driver tool further comprises a wheel assembly. The tool is movable between an operating position having the base plate positioned against the media and a transport position having the wheel assembly positioned against the media so as to provide manual portability for the tool. The wheel assembly may be offset from the media in the operating position so as to increase stability for the tool. The base plate may be offset from the media in the transport position so as to increase portability of the tool. The driver tool may also have a brace that is deployed in the operating position to enhance the stability of the tool. The brace is folded against the tool in the transport position to enhance the portability of the tool. 
     Another aspect of the present invention is a method of installing a shaft into a surrounding media comprising the steps of providing motorized movement of a powered hammer along a tower, stabilizing the tower generally perpendicularly to the media, positioning the shaft proximate the tower lengthwise between the hammer and the media, and driving the shaft with the hammer into the media. The stabilizing step may comprise the substeps of attaching the tower to a generally planar base plate so that the tower extends in a direction normal to the base plate, and placing a face of the base plate against the media. The positioning step may comprise the substeps of providing an open-faced slot in the base plate and locating the shaft within the slot. The driving step may comprise the substeps of raising the hammer along the tower and away from the media so as to enable a first end of the shaft to be positioned near the hammer and a second end of the shaft to be positioned against the media and positioning the hammer so as to contact the shaft with a bit installed in the hammer. Further substeps are actuating the hammer so as to repeatedly strike the shaft with the bit and lowering the hammer along the tower and toward the media during the actuating step so as to maintain contact between the bit and the shaft. 
     Yet another aspect of the present invention is a driver tool for installing a shaft into a media comprising a base means for supporting the tool and accommodating the shaft, a hammer means for repeatedly striking the shaft, and a tower means attached to the base means for movably retaining the hammer means. The driver tool may further comprise a motor and a positioning means actuated by the motor for moving the hammer means along the tower means. Also, the driver tool may comprise a control means for independently routing power to the hammer means and the motor. The driver tool may further comprise a transport means for manually moving the tool. 
     The driver tool of the present invention has many advantages over present methods of installing injection casings and other shaft media into the ground. Because the hammer is slidably mounted to a tower, it eliminates the need of an operator handling this heavy piece of equipment. The tower allows the hammer to be precisely positioned on a casing end several feet above ground-level, eliminating the need for an operator to stand on a platform, with the associated safety risks. Unlike heavy equipment used for driving shafts into the ground, the driver tool is compact for operation in limited access areas and can utilize relatively small shaft sections compared with heavy equipment. The mounted turf tires and the size and balance of the driver tool allow portability by one or two men. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a front perspective view of the driver tool illustrating its operating position with the hammer lowered; 
     FIG. 1B is a rear perspective view of the driver tool corresponding to FIG  1 A; 
     FIG. 2 is a front view of the driver tool illustrating its operating position with the hammer raised; 
     FIG. 3 is a side view of the driver tool illustrating its transport position; 
     FIG. 4 is a side view of the driver tool illustrating the motor, gears and drive chain; 
     FIG. 5 is an expanded side view of the driver tool corresponding to FIG. 4; 
     FIG. 6 is an expanded rear view of the driver tool illustrating the air filter and regulator; 
     FIG. 7A is a front perspective view of the driver tool illustrating an injection casing positioned within the base plate and the hammer in a raised positioned with its bit loaded on the unattached end of an injection casing; 
     FIG. 7B is another front perspective view of the driver tool illustrating the hammer in a partially lowered position and the injection casing partially driven into its surrounding media during installation; and 
     FIG. 7C is a front view of the driver tool illustrating an installed casing and the hammer in its fully raised position for attachment of another injection casing section. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A and 1B illustrate the operating position of the driver tool  100  according to the present invention. The driver tool  100  has a chassis  110 , a tower  120 , a hammer  130 , a drive chain  140 , a control assembly  150 , a front wheel assembly  160  and a rear wheel assembly  170 . The tower  120  is attached to the chassis  110  at several locations. The hammer  130  is mounted to the chain assembly  140 , which moves the hammer up and down along the tower  120 . The hammer  130  is shown lowered at its farthest extent along the tower  120 . Hammer movement is accomplished with the chain assembly  140  at a direction and rate determined by a tool operator using the control assembly  150 . The front  160  and rear  170  wheel assemblies are mounted on the chassis  110 . In the tool&#39;s transport position (FIG.  3 ), the chassis  110  rests on the wheel assemblies  160 ,  170 . In the tool&#39;s operating position, the wheel assemblies  160 ,  170  are not in contact with the ground, advantageously improving tool stability. 
     As shown in FIGS. 1A-1B, the chassis  110  has an open-face base plate  112 , a retracting ground or floor brace  114 , a motor box  116  and handles  118 . The base plate  112  has an open-face slot  720  configured to accommodate injection casings during installation. When deployed, as shown in FIGS. 7A-B and described below, the brace  114  pivots away from the chassis and is positioned against the ground and locked in place to increase tool stability during operation. The motor box  116  contains a motor  410  (FIG. 4) that powers the drive chain  140 . The handles  118  and balance of the tool  100  allow a person to move the tool  100  between its operating position and transport position without assistance. The handles  118  also allow one or two persons to easily move the tool  100  in its transport position. 
     In one embodiment, the tower  120  has a height in the range of between 94″ and 116.″ A tower height at the low end of that range advantageously allows driver tool accessibility to confined spaces, such as inside a structure with 8′ high ceilings. Such a tower, however, would only accommodate shorter shaft sections, such as 4′ length casings. A tower height at the high end of that range advantageously allows the use of longer shaft sections, such as 5′ to 6′ length casings, requiring fewer sections to be attached and removed during a grouting operation, for example, in comparison to a driver tool with a shorter tower. 
     Also shown in FIGS. 1A-B, the tower  120  is attached to the base plate  112 . In addition to supporting the tower  120 , the base plate  112  functions to supply stability and balance to the driver tool  100 , advantageously requiring minimal support, if any, from the tool&#39;s operator. During operation, the base plate  112  is positioned flush against the ground, where its substantial weight and relatively large footprint provide a stable low center-of-gravity for the tool  100  and resistance to lateral movement. The large base plate footprint also prevents the tool from sinking into soft earth. A further base plate feature is an open-face slot  720  that accommodates shafts. This feature utilizes a shaft  710  (FIGS.  7 A-C), such as an injection casing, to provide further driver tool stability. The open-face design also facilitates removing the driver tool from an installed shaft by simply moving the driver tool  100  away from the shaft  710  (FIGS. 7A-C) so that the shaft slides out of the open-face slot  720 , eliminating the need to lift a heavy apparatus over the top of an installed shaft. 
     In one embodiment, the tower  120  is 9″ wide and is attached to a base plate  112  constructed of 1″ hot rolled steel having a 23″ depth, 23″ front width, 15½″ back width and weighing about 90 lbs. The tower  120  can be constructed of {fraction (3/16)}″ hot rolled steel having a 4″ channel. A suitable hammer  130  is a Thor®  125  Breaker available from Champion Tool &amp; Supply, Riverside, Calif., modified to replace the handle with a mounting bracket. Ignoring the open-face slot  720 , the base plate  112  has an area of approximately 470 sq. in. The open-face slot  720  has a 7¾″ length and a 3″ width. The slot  720  ends in a semi-circular shape having a diameter matching the slot width. The dimensions of the open-face slot  720  advantageously accommodate 1½″ schedule  80  injection casings having 2⅛″ outer diameters. These casings are loose enough so that casings are easy to position within the driver tool  100 , yet tight enough so that the casings provide support and stability to the tool. 
     FIG. 2 also shows the driver tool  100  in its operating position. In contrast with FIGS. 1A-1B, the tool  100  is shown with the hammer  130  raised at its farthest extent along the tower  120 . The tower  120  retains the drive chain  140  and a mounting plate  210 . The mounting plate  210  is attached to the drive chain  140 . The hammer  130  is attached to the mounting plate  210 , which can slide along the length of the tower  120  as determined by movement of the drive chain  140 . Note that a handle (not shown) may be attached to the mounting plate  210  so that an operator standing at the front of the driver tool  100  can further stabilize the driver tool  100  during operation. 
     FIG. 3 shows the driver tool  100  in its transport position. With the hammer  130  in its raised position (FIG.  2 ), the tool  100  is sufficiently balanced so that it can be moved from its operating position (FIG. 1A) to its transport position by one person. In the transport position, the tool is supported by turf tires  310  mounted on the front and rear wheel assemblies  160 ,  170 . The front wheel assembly  160  has brakes (not shown) that, when set, prevent the front wheel assembly  160  from rotating. This facilitates moving the tool  100  between the transport and operating positions. Suitable tires  310  are sized 18.5″×8.5″×8″, such as item number 1219-G051, available from Northern Hydraulics, Burnsville, Minn. The tires  310  are mounted on wheels and axles, which are available as an ATV Tire, Wheel, Hub and Axle Kit, item number 135012-G051, also from Northern. An attachment bracket (not shown) may be located on the tower  140  (FIGS. 1A-B) so that the driver tool  100  may be conveniently transported by a skipsteer loader or any tool with an excavating bucket attachment. 
     FIG. 4 shows the drive chain  140 , the control assembly  150  and inside the motor box  116  revealing the motor  410  and the reduction gear  420 . The drive chain  140  is shown engaged upon a combination of the reduction gear  420 , an upper sprocket  430 , a lower sprocket  440  and a motor box sprocket  450 . The lower sprocket  440  is mounted to a tension adjuster  460  used to manually set the drive chain tension. The tension adjuster  460  may also advantageously incorporate a tension spring  590  (FIG. 5) to absorb mechanical force, such as vibration, that is otherwise transferred to the drive chain  140  during operation of the hammer  130 . 
     One of ordinary skill in the art will recognize other linking mechanisms besides the drive chain  140  for transferring mechanical energy from the motor  410  to the hammer  130  in order to move the hammer  130  along the tower  120 . For example, the mounting plate  210  could be threaded onto a jack screw that is installed within the tower  120  and rotated by the motor  410 . As another example, the motor  410  could be installed on the mounting plate  210  with a geared drive shaft that engages teeth along the length of the tower  120 . 
     FIG. 5 shows further detail of the control assembly  150  and the motor  410 . The control assembly  150  has two valves, a dual-port valve  510  and a single-port valve  520 . The dual-port valve  510  directs air pressure to either a first hose  512  or a second hose  514  as determined by the motor direction control handle  540 . Pressure into the first hose  512  rotates the motor in a first direction, causing the gear  420  to turn counterclockwise and raising the hammer  130 . Pressure into the second hose  514  rotates the motor in a second direction, causing the gear  420  to turn clockwise, lowering the hammer  130 . The single-port valve  520  directs pressure into the hammer hose  522  as determined by the hammer control handle  570 , actuating and de-actuating the hammer. Advantageously, pressing down simultaneously on both the motor direction control  540  and the hammer control  570  both lowers and actuates the hammer  130  so as to drive an injection casing into the ground at rate controllable by an operator using one hand. Power can be supplied to the driver tool  100  and in particular to the hammer  130  and the motor  410  by an external power unit or “mule” (not shown) that generates compressed air at a suitable pressure. 
     The reduction gear  420  has a gear ratio that provides a hammer movement slow enough for easy controllability and fast enough for reasonably quick shaft installation. In one embodiment, the reduction gear  420  has a gear ratio in the range of 50:1 to 70:1. A suitable reduction gear  420  is a model C70-HS gear box having a 60:1 gear ratio available from Toledo Gearmotor Company, Sylvania, Ohio. A suitable motor  410  is a model 4AM-NRV-570C air motor available from GAST Mfg. Inc., Benton Harbor, Mich. A suitable control assembly  150  is a model 201626-B938 4 way, 4 position 3500 psi direction control valve with spring center and float detent available from Prince Hydraulics, Sioux City, Iowa. Note that a two-way check vent (not shown) can be installed in the second hose  514  so that when the hammer is lowered, moisture can be vented to avoid accumulation in the motor. 
     FIG. 6 shows an air filter  610  and an air pressure regulator  620 . Air pressure from a generator (not shown) is supplied via a hose connected to one end  612  of the air filter. The other end of the air filter  614  is attached to the regulator  620 . In turn, the regulator  620  supplies a lowered, controlled air pressure to the control assembly  150 . 
     Although the above embodiments are described in terms of a pneumatic hammer and motor, one of ordinary skill in the art will recognize that the drive tool  100  and in particular the hammer  130  and the motor  410  can be configured to operate from other externally generated power sources, such as pressurized hydraulic fluid or electricity. Alternatively, the drive tool  100  can be internally powered by a fuel, such as a gasoline motor to move or actuate the hammer  130 . 
     FIGS. 7A-C illustrate operation of the driver tool  100 . FIG. 7A shows the tool  100  with the hammer  130  in a fully raised position. A shaft  710  is accommodated within the open-face slot  113  of the base plate  112 . A bit  730  is attached to the hammer  130  and positioned at one end  712  of the shaft  710 . A suitable bit  730  for use in driving injection casings is a one-piece pipe driver having a 1⅛″ or 1¼″ shank and a tip that fits within 1½″ casings, available from Vulcan Tools, South Hingham, Mass. The brace  114  is deployed to support the tool  110  against the ground in conjunction with the base plate  112 . FIG. 7B shows the hammer  130  in a partially lowered position after the control valves  540 ,  570  are pushed down to actuate and lower the hammer  130 , driving the injection casing  710  into the ground. FIG. 7C shows the hammer  130  in a fully raised position so that another section of injection casing may be attached to the protruding end of the previously installed casing  710 . 
     The portable injection-casing driver has been disclosed in detail in connection with various embodiments of the present invention. These embodiments are disclosed by way of examples only and are not to limit the scope of the present invention, which is defined by the claims that follow. One of ordinary skill in the art will appreciate many variations and rodifications-within the scope of this invention.