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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of application Ser. No. 10/430,303, filed May 7, 2003. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to excavating. In particular, this invention relates to a system and method for excavating a roadway or other finished surface. 
     BACKGROUND OF THE INVENTION 
     Excavation is a necessary part of the repair procedure for many types of services which run under roadways, parking lots and other finished surfaces, for example a gas or water line running underneath a road or sidewalk. Traditionally, a jackhammer or trimack are used to break up the concrete or asphalt and an excavating machine such as a backhoe would remove the surface cover and uncover the service requiring maintenance and repair. The repair or other servicing would be effected, the excavation backfilled, and the surface refinished using a comparable material (asphalt, concrete, etc. as required to blend in with the surrounding surface finish). 
     This type of excavation is costly, in terms of both the inconvenience which results from having to remove and refinish a large portion of the road, sidewalk or other finished surface, particularly for example on a busy roadway, and the size of the hole which must be repaired following servicing. Many repair and maintenance procedures do not require a large excavation, and very localized access is sufficient to enable work crews to affect the service procedure. However, conventional excavating machinery is incapable of excavating with the precision required to provide only the opening necessary to access the service being repaired. 
     Accordingly, an excavating system comprising a rotary cutter mounted on a truck has been developed for performing what is commonly known as a “keyhole” excavation. The cutter is effectively a large hole saw, which cuts a circular “coupon” or “core” out of the finished surface allowing localized access to the service requiring maintenance or repair, mounted to a motor which is in turn mounted on a large drill press. 
     In such a keyhole excavation device the rotary cutting tool is mounted on a turret so that it can be positioned at various angles about the truck. A hydraulic actuator operates the press, forcing the rotating cutting head into the finished surface at a controlled rate to cut the core. Once the cutting head has penetrated the surface it is retracted to remove the core, and the core is placed aside. The opening is excavated down to the depth of the pipe in need of servicing using conventional vacuum technology, the repair or other service procedure effected, and the opening is backfilled. The core is then placed on a bed of bonding agent to refinish the surface. When the bonding agent hardens, the core has been reintegrated with the surface and in all cases the separation of the core from the surrounding surface will be barely noticeable. The savings of time and avoidance of inconvenience by effecting repairs and servicing through such keyhole excavation, and especially the savings in restoration costs, is significant. 
     The keyhole excavation is often required beside a roadway which may not be fully accessible to the truck, so the rotary cutter head is mounted on an arm which can move about the truck on a turret within an arc of approximately 270°. This allows the cutting head to be positioned along either side of the truck, or along the back of the truck, which permits some flexibility in the positioning of the truck, to ensure that the truck is in a stable position before cutting commences. For example, the truck can be positioned on the shoulder of a road, or within one lane, so as to minimize the disruption of vehicular traffic. 
     However, the vertical hydraulic press assembly used to force the cutting head into the finished surface is supported on a horizontal arm which has a single stabilizing point, i.e. at the turret, and it is accordingly difficult to keep the press—and thus the cutter—stable during drilling. Imperfections in the cutting head and obstructions in the finished surface cause the support arm to vibrate. These vibrations are transferred to the vertical press, which causes the support arm to shift about the drilling access which in turn causes the vibration to increase. The resulting instability makes cutting difficult in some cases, and limits the size and depth of the rotary cutter head because a deeper rotary cutter head both causes greater vibration and, due to the greater distance between the cutting edge and the shaft, shifts more under the influence of the vibration. 
     It would accordingly be advantageous to provide a more stable system and method for cutting a core out of a finished surface as part of a keyhole excavation process. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes these disadvantages by providing a system and method of cutting a core out of a finished surface for keyhole excavation which results in a stable cutting procedure with less vibration. This makes the keyhole excavation procedure safer and more precise, and allows a larger-depth cutting head to be used in order to penetrate thicker finished surfaces. 
     The invention accomplishes this by providing a stabilizing member remote from the turret, which allows the turret to be rotated about its complete arc while stabilizing the support arm at each position within the turret&#39;s arc of motion. 
     In a first embodiment an apparatus according to the invention comprises an upstanding support rim affixed to or integrated into the bed of the truck, which approximates the height of the turret and forms a secondary support remote from the turret. In a further embodiment in the invention comprises a support member affixed to the horizontal arm, for example a strut or brace moveable along and supported by the truck bed. 
     In the preferred embodiment the cutter head is provided with a pilot, which guides the cutter head during the cutting operation. The pilot also creates a pilot hole in the core that both facilitates removal, manipulation and replacement of the core, and improves the integrity of the reinstated core because the reinstatement compound intrudes into the pilot hole and sets to form a vertical bridge structure that provides vertical support and resistance to lateral shifting. 
     The present invention thus provides a system for cutting an opening in a paved surface, comprising: a truck having a bed; a support arm mounted on a turret supported by the truck, a cutter press mounted on the support arm, being moveable from a generally horizontal position to a generally vertical position, a rotary cutter comprising a motor and a cutter head mounted on the cutter press for cutting a replaceable core out of the paved surface such that the core remains in substantially the same condition for reinstatement into the paved surface, and a secondary support for supporting the support arm at a position remote from the turret. 
     The present invention further provides a method of cutting an opening through a paved surface, comprising the steps of: a) rotating a turret to position a cutter head supported on a support arm over a desired location of the opening, b) rotating the cutter head, c) supporting the support arm at a position remote from the turret, d) pressing the cutter head into the paved surface, e) removing the core from the paved surface; and f) reinstating the core into the paved surface in substantially the same condition as when it was removed from the paved surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In drawings which illustrate by way of example only a preferred embodiment of the invention, 
         FIG. 1  is a schematic side elevation of a first embodiment of the invention showing the drill press in a storage position; 
         FIG. 2  is a schematic side elevation of the embodiment of  FIG. 1  showing the drill press in a drilling position; 
         FIG. 3  is a schematic side elevation of the embodiment of  FIG. 1  showing the cutter drilling through a surface; 
         FIG. 4  is a schematic side elevation of a further embodiment of the invention having a support member affixed to the support arm; 
         FIG. 5  is a schematic top plan view of the embodiment of  FIG. 1 ; 
         FIG. 6  is a schematic top plan view of the embodiment of  FIG. 4 ; 
         FIG. 7  is an enlarged elevation of a locking mechanism for the embodiment of  FIG. 4 ; and 
         FIG. 8  is a top plan view of the core after the cutting operation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 3  illustrate a first embodiment of the system of the invention. A truck  10  comprising a back portion, preferably having a flat bed  12 , is provided with a rotary turret  14  which supports the cutter assembly  20 . The turret  14  is driven by a worm gear (not shown) mounted to the bed  12  understructure and decking, and operated by a built in or remote pendant control (not shown). The hydraulic pump  16  is mounted to the bed  12  immediately behind the cab  11  of the truck  10 . The bed  12  is otherwise unobstructed, to allow for a large arc of motion of the cutter assembly  20 , as described below. 
     The cutter assembly  20  is mounted to the turret  14 . The cutter assembly  20  comprises a horizontal support arm  22 , which may for example be composed of steel bar or tubing or another suitable material, extending sufficiently beyond the periphery of the truck  10  to support the vertical cutting press  30  (described below) at a position which allows it to clear the rear corners of the bed  12 . The turret  14  is accordingly preferably positioned equidistant from the rear edge of the bed  12  and the side edges of the bed  12 , as shown in  FIG. 5 . 
     The cutter press  30  comprises a frame  32  supporting a hydraulic cylinder  34  having a piston  36  fixed to sliding frame  33  to which the cutter motor  40  is mounted. The piston  36  preferably provides approximately a 30″ drill stroke for an 18″ depth core, which allows the pilot bit  44  to be positioned with sufficient clearance above the surface before cutting while allowing the cutter head  42  to penetrate to its entire depth before the press  30  bottoms out. A water tank  38  is mounted to the top end of the frame  32 , to supply coolant to the cutter head  42  when in use. 
     The supporting member, comprising a ledge or raised edge  50  (best seen in  FIG. 5 ), circumscribes a sufficient portion of the periphery of the bed  12  that the horizontal arm  22  can rotate throughout its entire range of motion (approximately 270°) with the support arm  22  supported on the raised edge  50 . The raised edge  50  thus provides a secondary support point, which acts in conjunction with the turret to provide two-point stabilization of the horizontal support arm during the cutting process. This has the effect of reducing the cantilever of the support arm  22 , to thus reduce the “play” in the support arm  22  and, commensurately, its susceptibility to vibration. The secondary support point also dampens any vibration which is transferred to the support arm  22 . 
     In operation, the truck  10  is manoeuvred to a convenient position for cutting, and rear stabilizer legs  13  actuated by the hydraulic pump  16  are set into position to stabilize the truck  10 . The cutter assembly  30  is in the storage position shown in  FIG. 1 . The operator rotates the turret at least 45°, so that the distal end of the horizontal support arm extends beyond the periphery of the truck bed  12 . The operator pivots the cutter assembly  30  to a substantially vertical position, and aligns the pilot  44  over the center of the opening to be cut. The operator actuates the hydraulic pump to force the piston  36  out of the cylinder  34  and thus force the pilot  44  into the surface. When the teeth of the rotary head  42  contact the surface, the operator opens a valve to start coolant flowing from the tank  38  into the cutter head  42 . The water is preferably communicated to the cutter head and pilot by an electric water pump (not shown). 
     The operator monitors the cutter head  42  as it progresses through the finished surface. When the core  70  breaks free, the operator stops the cutter motor  42  and actuates the hydraulic pump  38  to retract the piston  36  into the cylinder  34  and remove the core  70  from the finished surface  2 . The operator rotates the turret to move the cutter assembly  30  away from the opening so that the material below the finished surface can be excavated. A plate (not shown) may be provided in the cutter head, supported on the pilot  44 , which can be pushed by a pole (not shown) extending through an opening in the top of the cutter head  42 , to force the core  70  out of the cutter head if necessary without damaging the core  70 . 
     In the embodiment illustrated in  FIGS. 4 and 6 , the support member comprises a brace  60  welded or otherwise suitably affixed to the horizontal support arm and extending down to the truck bed  12 . The brace  60  is lodged in a groove or track  62  formed in the truck bed  12 , which restrains the lower end of the brace  60  against horizontal motion. In the preferred embodiment, a locking means, for example a handle  64  having a cam surface  64   a  (seen in  FIG. 7 ), can be rotated to bear against the bed  12  of the truck  10  and lock the support member  60  in the groove  62  between the cam  64   a  and a ledge  64   b  at a selected position for cutting. Any other locking means can be used. The operation is otherwise as described above. 
     During the cutting process, the horizontal support arm  22  is stabilized by two points of support: the turret, which supports the fixed end of the horizontal arm  22 , and the stabilizing member  50  or  60 , which supports the horizontal arm  22  at an intermediate point between the turret and the cutter assembly  30 . The support member  50  or  60  thus dampens vibrations being fed back into the horizontal support arm from the cutter head, increasing the stability of the cutter assembly  30  and thus facilitating the cutting of the core  70 . After the repair or other service procedure is complete, the core  70  is replaced in conventional fashion. 
     The pilot  44  guides the cutter head  42  during the cutting operation, and also creates a pilot hole  72  in the core  70 , illustrated in  FIG. 8 . The pilot hole  72  facilitates removal, manipulation and replacement of the core  70 . The pilot hole  72  also improves the integrity of the reinstated core  70 , because the reinstatement compound is applied wet and as the core  70  is lowered into the hole the compound intrudes into the pilot hole  72  and then sets, forming a vertical bridge structure (not shown) that adheres to the pilot hole  72 , providing both vertical support and resistance to lateral shifting. 
     Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.

Summary:
A system and method of cutting for replacement a replaceable coupon out of a paved surface for keyhole excavation provides a truck with a turret to which a support arm supporting a cutter assembly is mounted, and a stabilizing member remote from the turret, which allows the turret to be rotated while stabilizing the support arm at any desired position about the truck.