Patent Publication Number: US-8967729-B1

Title: Trip hazard removal system and method

Description:
FIELD OF THE INVENTION 
     This invention relates generally to trip hazards, and, more particularly, to a system and method for systematically cutting trip hazards from concrete surfaces. 
     BACKGROUND 
     The Americans with Disabilities Act (ADA) of 1990 defines a ‘trip hazard’ as any vertical change of over ¼ inch or more at any joint or crack. Since the ADA demands strict compliance, trip hazards represent a legal liability to businesses. Cities, school districts, hospitals, churches, shopping malls, universities, apartment complexes, and other large building owners have good reason to be extremely concerned with trip hazards, the risk of injury to pedestrians and the attendant liability exposure. 
     One prior method to remove trip hazards is replacement. The affected concrete is demolished, removed, and replaced with a level surface. Unfortunately, such approach is time-consuming, expensive and disruptive. The walkway is rendered unusable for considerable time. The cost of replacement greatly exceeds the cost of repair. In many cases, replacement yields considerable waste, as the concrete which was otherwise intact is demolished and discarded. 
     Other past efforts to remove trip hazards entail manually grinding or cutting the protruding trip hazard. While such efforts may be effective for removing a trip hazard, they tend to be time-consuming and inefficient, extremely imprecise, scattering considerable concrete dust, and resulting in uneven surfaces. 
     What is needed is a controlled saw-cutting system and methodology that completely and cleanly removes trip hazards from sidewalks and similar walkways, from edge to edge, providing a safe walkway and virtually eliminating claims that result from trips and falls on uneven sidewalk. 
     The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above. 
     SUMMARY OF THE INVENTION 
     To solve one or more of the problems set forth above, in an exemplary implementation of the invention, a saw assembly controllably moves in a cutting plane defined by two orthogonal axes. An exemplary saw assembly includes a circular toothed blade that is configured to cut concrete and similar materials. A motor, such as a hydraulic motor, rotatably drives the saw blade. An adjustable shroud substantially surrounds the blade and confines dust and debris. A vacuum port of the shroud connects to a dust-removal vacuum via a hose. 
     A gantry supports the saw assembly, controls movement of the saw assembly and defines the cutting plane. The gantry comprises a framework with rails defining axes of motion. Pairs of spaced apart parallel rails comprise tracks, which define each axis of motion. Linear actuators control motion along the axes. Legs of the gantry establish a cutting plane. 
     The gantry may be mounted to a utility vehicle in a manner that allows deployment for use and stowing for storage and transportation. The mounting may comprise pivoting joints. A winch attached to the gantry may raise and lower the gantry. In the raised position, the gantry is stowed for storage and transportation. In the lowered position, the gantry is deployed for cutting use. The utility vehicle may include a hydraulic pump and an air compressor for powering a hydraulic motor and a pneumatic actuator. The utility vehicle may also include a dust collection vacuum for collecting dust and debris. 
     Rollers coupled to the saw assembly facilitate linear translation of the saw assembly along a first axis. Each roller includes a V-shaped notch which rides against an angled rail. A pair of spaced apart parallel angled rails define the first axis of motion, and are collectively referred to as the first track. 
     The first track is movable along a second axes, which is orthogonal to the first axis. The parallel angled rails that define the first axis and comprise the first track are coupled to rollers that facilitate linear translation of the saw assembly along the second axis. A pair of spaced apart parallel angled rails define the second axis of motion, and are collectively referred to as the second track. 
     Movement along the first and second tracks is effectuated with linear actuators. In one embodiment, movement along the first track is effectuated using a pneumatic actuator, while movement along the second track is effectuated with a chain drive. The pneumatic actuator thus controls plunge cutting action of the saw assembly, while the chain drive controls side to side cutting action of the saw assembly. 
     In one embodiment, an exemplary walkway surface cutting system for removing a trip hazard from a walkway is provided. The walkway including a trip hazard (e.g., a raised portion) and a walkway surface without a trip hazard (e.g., the surrounding portions of the walkway. The trip hazard is higher than the walkway surface without the trip hazard. The system includes a gantry having a support framework including a first track and a second track. The first track is linearly movable along and orthogonal to the second track. A saw assembly includes a motor and a masonry saw blade (e.g., a blade suitable for cutting stone and/or concrete) operably coupled to and driven by the motor. The saw assembly is linearly movable along the first track. A support maintains the gantry at a cutting height and cutting angle relative to a portion of the walkway not to be cut. The cutting height and cutting angle is at a height and angle for the saw blade to cut the trip hazard without cutting the walkway surface without a trip hazard. A first linear actuator is operably coupled to the saw assembly. The first linear actuator includes a first stationary body and a first shaft controllably extendible from and retractable into the first stationary body. Extension of the first shaft causes linear movement of the saw assembly along the first track in a first direction. Retraction of the first shaft causes linear movement of the saw assembly along the first track in a second direction opposite the first direction. A second linear actuator is operably coupled to the first track. The second linear actuator includes a linearly moveable element and a control. Manipulation of the control causes linear movement of the linearly moveably element and the first track with the saw assembly along the second track. 
     The gantry has a front side and a back side, a right side and a left side. Cutting motion of the saw assembly progresses between front side and back side along the first track, and between left side and right side along the second track. Front to back motion is for plunging the saw blade into the trip hazard. Motion between the right and left sides is to sweep the saw blade along the width of the trip hazard. 
     In one embodiment the gantry is attached to a utility vehicle. A hinge couples the front of the gantry to the utility vehicle, e.g., to a bed of the utility vehicle. The gantry is pivotable about the hinge from a deployed position to a stowed position. A hoisting apparatus coupled to the utility vehicle and gantry and pivots the gantry between the deployed position and the stowed position. In one embodiment, the hoisting apparatus includes a manual or motorized winch attached to the utility vehicle and a tether (e.g., cable) extending from a spool of the winch to the gantry. 
     The support may include a back leg attached to the gantry adjacent to the back of the gantry and a front leg attached to the gantry adjacent to the front of the gantry. The front leg may be fixed in length and the back leg may be adjustable in length. The front leg may be fixed in length and the back leg may be a removable leg of a selectable length. The back leg may be fixed in length and the front leg may be adjustable in length. The back leg may be fixed in length and the front leg may be a removable leg of a selectable length. More than one back leg and front leg may be provided. 
     In one embodiment, the motor of the saw assembly is a hydraulic motor. A hydraulic pump (e.g., an engine driving a gear pump) supplies hydraulic fluid to the hydraulic motor. 
     In one embodiment, the first linear actuator is a pneumatic actuator. A control valve pneumatically coupled to the first linear actuator controls a flow of compressed air to the linear actuator from an air compressor. 
     In one embodiment, the second linear actuator is a chain drive. The chain drive includes a chain trained around a drive cog and a driven cog and having a straight segment extending therebetween. The straight segment of the chain is coupled to the first track. A shaft extends from the drive cog. A handle on the shaft allows control. Rotation of the handle causes rotation of the drive cog, which causes linear movement of the straight segment. 
     In one embodiment, a shroud (e.g., debris shield) is provided above the saw blade. The shroud includes a vacuum port coupled to a vacuum hose coupled to a vacuum for dust collection. A shield vertically movable relative to the shroud under the influence of contact with the walkway guards against propelled debris and helps to constrain dust from cutting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other aspects, objects, features and advantages of the invention will become better understood with reference to the following description, appended claims, and accompanying drawings, where: 
         FIG. 1  is a side view of an exemplary saw assembly according to principles of the invention; and 
         FIG. 2  is a plan view of an exemplary saw assembly according to principles of the invention; and 
         FIG. 3  is a top perspective view of an exemplary saw assembly according to principles of the invention; and 
         FIG. 4  is a bottom perspective view of an exemplary saw assembly according to principles of the invention; and 
         FIG. 5  is a plan view of an exemplary saw gantry according to principles of the invention; and 
         FIG. 6  is a back view of an exemplary saw gantry according to principles of the invention; and 
         FIG. 7  is a side view of an exemplary saw gantry according to principles of the invention; and 
         FIG. 8  is a first perspective view of an exemplary saw gantry according to principles of the invention; and 
         FIG. 9  is a second perspective view of an exemplary saw gantry according to principles of the invention; and 
         FIG. 10  is a perspective view of an exemplary roller and angled track for a saw gantry according to principles of the invention; and 
         FIG. 11  is a plan view of an exemplary utility vehicle equipped with a saw gantry according to principles of the invention; and 
         FIG. 12  is a side view of an exemplary utility vehicle equipped with a saw gantry in a deployed position according to principles of the invention; and 
         FIG. 13  is a side view of an exemplary utility vehicle equipped with a saw gantry in a stowed position according to principles of the invention; and 
         FIG. 14  is a perspective view of an exemplary utility vehicle equipped with a saw gantry in a deployed position according to principles of the invention; and 
         FIGS. 15 ,  16 , and  17  are schematics that conceptually illustrate a step of an exemplary method of repairing a sidewalk according to principles of the invention; and 
         FIGS. 18 ,  19 , and  20  are schematics that conceptually illustrate another step of an exemplary method of repairing a sidewalk according to principles of the invention; and 
         FIGS. 21 ,  22 , and  23  are schematics that conceptually illustrate yet another step of an exemplary method of repairing a sidewalk according to principles of the invention. 
     
    
    
     Those skilled in the art will appreciate that the figures are not intended to be drawn to any particular scale; nor are the figures intended to illustrate every embodiment of the invention. The invention is not limited to the exemplary embodiments depicted in the figures or the specific components, configurations, shapes, relative sizes, ornamental aspects or proportions as shown in the figures. 
     DETAILED DESCRIPTION 
     In general, an exemplary system according to principles of the invention comprises a saw assembly that controllably moves in a cutting plane along two orthogonal axes. An exemplary saw assembly includes a circular toothed blade that is configured to cut concrete and similar materials. A motor, such as a hydraulic motor, rotatably drives the saw blade. An adjustable shroud substantially surrounds the blade and confines dust and debris. A vacuum port of the shroud connects to a dust-removal vacuum via a hose. 
     A gantry supports the saw assembly, controls movement of the saw assembly and defines the cutting plane. The gantry comprises a framework with rails defining axes of motion. Pairs of spaced apart parallel rails comprise tracks, which define each axis of motion. Linear actuators control motion along the axes. Legs of the gantry establish a cutting plane. 
     The gantry may be mounted to a utility vehicle in a manner that allows deployment for use and stowing for storage and transportation. The mounting may comprise pivoting joints. A winch attached to the gantry may raise and lower the gantry. In the raised position, the gantry is stowed for storage and transportation. In the lowered position, the gantry is deployed for cutting use. The utility vehicle may include a hydraulic pump and an air compressor for powering a hydraulic motor and a pneumatic actuator. The utility vehicle may also include a vacuum for collecting dust and debris. 
     Rollers coupled to the saw assembly facilitate linear translation of the saw assembly along a first axis. Each roller includes a V-shaped notch which rides against an angled rail. A pair of spaced apart parallel angled rails define the first axis of motion, and are collectively referred to as the first track. 
     The first track is movable along a second axes, which is orthogonal to the first axis. The parallel angled rails that define the first axis and comprise the first track are coupled to rollers that facilitate linear translation of the saw assembly along the second axis. A pair of spaced apart parallel angled rails define the second axis of motion, and are collectively referred to as the second track. 
     Movement along the first and second tracks is effectuated with linear actuators. In one embodiment, movement along the first track is effectuated using a pneumatic actuator, while movement along the second track is effectuated with a chain drive. The pneumatic actuator thus controls plunge cutting action of the saw assembly, while the chain drive controls side to side cutting action of the saw assembly. 
     Referring now to  FIGS. 1 through 4 , an exemplary saw assembly  100  according to principles of the invention is conceptually illustrated. A motor  110  (e.g., hydraulic motor) is operably coupled to and rotatably drives a circular saw blade  105 . The blade is a circular blade suitable for cutting cutting concrete, masonry, brick, asphalt, tile, and other solid materials. Industrial diamonds are fixed on cutting edges of the blade. The coupling may comprise a drive shaft, gear train, belt or chain drive and combinations of the foregoing. While the saw may be powered by a gasoline, hydraulic, pneumatic, or electric motor, a hydraulic motor is preferred. Such a motor  110  includes at least two hydraulic fluid ports  115  and  120 , one serving as an inlet and the other as an outlet. The ports  115 ,  120  are coupled to a source of pressurized hydraulic fluid, such as a hydraulic pump, via hydraulic lines (i.e., hoses). 
     A forward shroud  125  and an aft shroud  130  cover the blade  105 . A flexible protective skirt  155  extends downwardly from the periphery of the forward shroud  125 . The skirt  155  guards against dust and debris propelled by the spinning circular saw blade  105 . The flexible skirt  155  may comprise brush bristles or flexible plastic elements. The saw blade  105  is exposed at the bottom of the skirt  155 . A floating rigid guard  145  is movably coupled to the aft shroud  130 . Pins  135  and elongated slots  140  in the guard  145  allow up and down movement of the guard  145 , while holding the guard  145  to the aft shroud  130 . Thus, the aft shroud may drop to the level of the walkway being cut. 
     A vacuum port  150  in the aft shroud  130  may be coupled to a hose leading to a vacuum for the collection of dust and debris. The vacuum port  150  is in communication with the cavity defined by the shroud  130  and guard  145  and shroud  125  and guard  155 , in which the blade  105  resides. Thus, dust and debris from cutting are removed from the cavity through the port  150  to a vacuum. 
     Referring now to  FIGS. 5 through 9  an exemplary saw gantry  200  according to principles of the invention is conceptually illustrated. The saw assembly  100  described above is shown roughly in the center of the gantry  200 . The gantry  200  supports the saw assembly  100 , controls movement of the saw assembly  100  and defines a cutting plane. The gantry  200  comprises a framework with pairs of parallel rails  210 ,  212  and  215 ,  217 , each pair defining an axis of motion. Each pairs of spaced apart parallel rails  210 ,  212  and  215 ,  217  comprise a track, which defines an axis of motion. Linear actuators  255 ,  270  control motion along the axes. 
     The saw assembly  100  is attached to parallel spaced apart support bars  225 ,  227 . Rollers  234 ,  236  are rotatably attached to support bar  225 . Rollers  238 ,  240  are rotatably attached to support bar  227 . One set of rollers  234 ,  236  travel along one rail  215 , while the other set of rollers  238 ,  240  travel along the spaced apart parallel rail  217 . Thus, linear translation of the saw assembly  100  along one axis (i.e., the first axis or plunge cut axis) is enabled. More specifically, the saw assembly  100  may move back and forth along the first track comprised of rails  215 ,  217 . The range of motion is determined in part by the length of the rails  215 ,  217 . In a preferred embodiment, the range of motion is at least (and preferably greater than) ½ of the diameter of the saw blade  105 , to enable plunge cutting. 
     The rails  215 ,  217  are attached at opposite ends to parallel spaced apart support bars  220 ,  222 . Rollers  230 ,  232  are rotatably attached to support bar  220 . Rollers  242 ,  244  are rotatably attached to support bar  222 . One set of rollers  230 ,  232  travel along one rail  210 , while the other set of rollers  242 ,  244  travel along the spaced apart parallel rail  212 . Thus, linear translation of the saw assembly  100  on along a second axis (or the side to side axis) is enabled. More specifically, the saw assembly  100  may move side to side along the second track comprised of rails  210 ,  212 . The range of motion is determined in part by the length of the rails  210 ,  212 . In a preferred embodiment, the range of motion is at least (and preferably greater than) the width of a walkway (e.g., 60 inches). However, the invention is not so limited. Rails  210 ,  212  providing less range of motion may be utilized, though multiple cuts may be required to extend across the entire width of a sidewalk. 
     The second track is orthogonal to the first track. The second axis is orthogonal to the first axis. The second axis is parallel to the second track. The first axis is parallel to the first track. The rails comprising the second track are parallel to the second axis. The rails comprising the first track are parallel to the first axis. 
     Linear actuators effect movement along the first and second tracks, and along their corresponding axes. In one embodiment, movement along the first track comprised of rails  215 ,  217  is effectuated using a pneumatic actuator  270 , while movement along the second track comprised of rails  210 ,  212  is effectuated with a chain drive  255 . The particular location of each linear actuator is not important, so long as it achieves the desired motion. 
     The pneumatic actuator  270  uses the power of compressed gas (e.g., air) to produce a force in a linear motion. The pneumatic actuator  270  is pneumatically coupled by air supply lines to a source of compressed air, such as an air compressor with a compressed air storage tank. The pneumatic actuator  270  may be double-acting to facilitate motion in either direction along the first axis. A valve  260  pneumatically coupled to the actuator  270  controls the flow of compressed air to the actuator  270 . A user controls the valve  260 . The pneumatic actuator  270  is mechanically coupled at one end to a forward rail  210 , and at its opposite end, via a pivoting joint  272 , to the saw assembly  100  or to the support bar  227 . The pneumatic actuator  270  controls plunge cutting action of the saw assembly, while the chain drive  255  controls side to side cutting action of the saw assembly. 
     A chain drive assembly effectuates side-to-side movement along the second track comprised of rails  210 ,  212 . The assembly includes a continuous chain  255  entrained around a first sprocket  250  and an opposite drive sprocket  252 . A shaft  256  extends from the drive sprocket  252  to a handle  254 . Turning the handle  254  rotates the drive sprocket  252 , which causes the chain  255  to move. The length of chain  255  between the sprockets  250 ,  252  moves in a linear fashion, one way or another, depending upon the direction of rotation. A coupling  275  connects the chain between the sprockets to the support bar  222 . Consequently, linear motion of the length of chain  255  between the sprockets  250 ,  252  causes the coupling  275  and attached support bar  222  to move linearly. Thus, rotation of the handle  254  in one direction, causes linear motion of the length of chain  255  between the sprockets  250 ,  252  in one direction, which causes the support bar  222  to travel along rail  212  in the same direction. Such linear motion of the support bar  222  causes, linear translation of the saw assembly  100  on along a second axis (or the side to side axis) is enabled. More rotating the handle  254  moves (linearly translates) the saw assembly  100  along the second track comprised of rails  210 ,  212 . The direction of movement is a function of the direction of rotation of the handle  254 . The speed of movement is a function of the rate of rotation of the handle  254  and the size of the drive sprocket  252 . 
     The gantry may be mounted to a utility vehicle in a manner that allows deployment for use and stowing for storage and transportation. The mounting may comprise pivoting joints  245 ,  247 , (e.g., hinges) each of which may be attached to a bed of a utility vehicle. Such joints allow pivoting deployment of the gantry from the bed of a utility vehicle. 
     Forward legs  280 ,  282  and an aft leg  257  establish a cutting plane. The aft leg  257  may be adjustable in height or replaceable with a leg of a desired length. An adjustable height leg may include telescoping portions. One segment of the leg may slide or thread from another receiving segment of the leg to adjust the height. A locking mechanism such as a pin may secure the leg at a desired length. The forward legs  280 ,  282  end at, meet and define the cutting plane. The length of the aft leg  257  defines the angle of the cutting plane. The saw blade  105  cuts in the cutting plane. 
     One or more attachments (e.g., D-rings  262 ,  265 ) are also provided. These attachments enable connection to a cable, chain, strap or other tether to winch or hoist the gantry  200  from a stowed position to a deployed position and from a stowed position to a deployed position. 
     In  FIG. 10 , a perspective view of an exemplary roller  232  and mating angled rail  210  for a track of a saw gantry according to principles of the invention is conceptually illustrated. An exemplary roller  232  is a hardened steel thrust-load-rated track roller with a v-groove that provides accurate positioning on a 90° angle rail. The rail  210  may comprise 90° steel angle iron with a welded backing for additional rigidity. Such a roller  232  facilitates linear translation along the rail  210 . 
       FIGS. 11 through 14  provide various views of an exemplary utility vehicle  300  equipped with a saw gantry  200  according to principles of the invention. In  FIGS. 11 ,  12  and  14 , the gantry  200  is shown in the deployed position. In the deployed position, the gantry extends outwardly from the hinges  245 ,  247  attached to the back of the truck bed  350 . In the stowed position as shown in  FIG. 13 , the gantry  200  is pivoted to an upright position. 
     A tether, such as a strap, cable or rope  337  is connected to attachments on the gantry. In the embodiment shown in  FIGS. 11-14 , the tether  337  is coupled to a pair of tethers  340 ,  345 , each of which connects to a D-ring  262 ,  265 . The tether  337  is wound from a spool of a winch  335 . Rotation of the spool in one direction winds up the tether  337 , pulling the gantry  200  to the stowed position. Rotation of the spool in one direction releases the tether  337 , dropping the gantry  200  to the deployed position. Thus, the winch  335  attached to the gantry  200  raises and lowers the gantry. In the raised position, the gantry  200  is stowed for storage and transportation. In the lowered position, the gantry  200  is deployed for cutting use. The winch may be manual, aulic or pneumatic. 
     The utility vehicle  300  may include an engine driven hydraulic pump  325 , and an air compressor  315  for powering a hydraulic motor  110  and a pneumatic actuator  270 . Hydraulic fluid is pumped from the pump  325  to a port  115 ,  120  of the motor  110  of the saw assembly  100  and back to the pump  325  via hydraulic hoses  330 . Compressed air is pumped from the compressor  315  to the pneumatic actuator  270  via pneumatic hoses  320 , controlled by valve  260 . The utility vehicle  300  may also include a vacuum  305  for collecting dust and debris via a vacuum hose  310  coupled to the saw assembly  100 . Electric power for the vacuum  305  and compressor  315  may be supplied by a battery in the vehicle  300 , by an electric generator or alternator of the vehicle  300 , or a supplemental electric power source. 
     A method of repairing a sidewalk or other walkway according to principles of the invention entails positioning the saw assembly, as illustrated in  FIGS. 15-17 . The saw assembly  100  is positioned with the cutting side, i.e., side  155 , facing the portion of the walkway to be cut. The saw assembly  100  is positioned at one side of the portion of the walkway to be cut. The forward legs  280 ,  282  are positioned forward of the cutting side  155  of the saw assembly  200 . The forward legs  280 ,  282  define the forward edge of the cutting plane cp. In other words, as the saw assembly  200  proceeds forward during a plunge cut, the plane in which the cut is made is the cutting plane cp. The cutting plane cp extends from the saw  105  to the forward legs  280 ,  282 . The angle θ of the cutting plane cp relative to the walkway to be cut is defined by the forward legs  280 ,  282  and the aft leg  257 . In a particular embodiment, forward legs  280 ,  282  are a fixed length and the length of the aft leg  257 , which is adjustable, defines the angle θ of the cutting plane—the longer the length of the aft leg  257 , the greater the angle θ of the cutting plane. From the initial position, the saw assembly may move towards the forward legs  280 ,  282  and towards the opposite side of the portion of the walkway to be cut, as illustrated by the dashed lines in  FIGS. 15 and 17 . 
       FIGS. 18 ,  19 , and  20  are schematics that conceptually illustrate a subsequent step of an exemplary method of repairing a sidewalk according to principles of the invention. In FIGS.  18 ,  19 , and  20  a plunge cut is made. A plunge cut is a cut into the portion of the walkway to be cut. The plunge cut is made by moving the saw assembly  100  towards the forward legs  280 ,  282 . The plunge is accomplished using the linear (pneumatic) actuator  270 , controlled by valve  260 . The depth of the plunge cut is defined by the forward motion of the saw assembly  100 . The depth of the plunge cut is not greater than the diameter of the saw blade  105 . Successive plunge cuts may be made if the portion to be cut away is appreciably greater in depth than the diameter of the saw blade  105 . 
       FIGS. 21 ,  22 , and  23  are schematics that conceptually illustrate yet another subsequent step of an exemplary method of repairing a sidewalk according to principles of the invention. In this step, the saw assembly  100  is moved from the plunge cut position towards the opposite side of the portion of the walkway to be cut. As the saw assembly moves, it cuts the walkway to the depth of the plunge cut from the initial plunge position to the opposite side. All the while, dust is collected by the vacuum  305  via vacuum hose  310 . The sideways motion of the saw assembly is accomplished using the chain drive  255 , controlled using handle  254 . 
     In sum, an exemplary walkway surface cutting system for removing a trip hazard from a walkway is provided. The walkway including a trip hazard (e.g., a raised portion) and a walkway surface without a trip hazard (e.g., the surrounding portions of the walkway. The trip hazard is higher than the walkway surface without the trip hazard. The system includes a gantry having a support framework including a first track and a second track. The first track is linearly movable along and orthogonal to the second track. A saw assembly includes a motor and a masonry saw blade (e.g., a blade suitable for cutting stone and/or concrete) operably coupled to and driven by the motor. The saw assembly is linearly movable along the first track. A support maintains the gantry at a cutting height and cutting angle relative to a portion of the walkway not to be cut. The cutting height and cutting angle is at a height and angle for the saw blade to cut the trip hazard without cutting the walkway surface without a trip hazard. A first linear actuator is operably coupled to the saw assembly. The first linear actuator includes a first stationary body and a first shaft controllably extendible from and retractable into the first stationary body. Extension of the first shaft causes linear movement of the saw assembly along the first track in a first direction. Retraction of the first shaft causes linear movement of the saw assembly along the first track in a second direction opposite the first direction. A second linear actuator is operably coupled to the first track. The second linear actuator includes a linearly moveable element and a control. Manipulation of the control causes linear movement of the linearly moveably element and the first track with the saw assembly along the second track. 
     The gantry has a front side and a back side, a right side and a left side. Cutting motion of the saw assembly progresses between front side and back side along the first track, and between left side and right side along the second track. Front to back motion is for plunging the saw blade into the trip hazard. Motion between the right and left sides is to sweep the saw blade along the width of the trip hazard. 
     In one embodiment the gantry is attached to a utility vehicle. A hinge couples the front of the gantry to the utility vehicle, e.g., to a bed of the utility vehicle. The gantry is pivotable about the hinge from a deployed position to a stowed position. A hoisting apparatus coupled to the utility vehicle and gantry and pivots the gantry between the deployed position and the stowed position. In one embodiment, the hoisting apparatus includes a manual or motorized winch attached to the utility vehicle and a tether (e.g., cable) extending from a spool of the winch to the gantry. 
     The support may include a back leg attached to the gantry adjacent to the back of the gantry and a front leg attached to the gantry adjacent to the front of the gantry. The front leg may be fixed in length and the back leg may be adjustable in length. The front leg may be fixed in length and the back leg may be a removable leg of a selectable length. The back leg may be fixed in length and the front leg may be adjustable in length. The back leg may be fixed in length and the front leg may be a removable leg of a selectable length. More than one back leg and front leg may be provided. 
     In one embodiment, the motor of the saw assembly is a hydraulic motor. A hydraulic pump (e.g., an engine driving a gear pump) supplies hydraulic fluid to the hydraulic motor. 
     In one embodiment, the first linear actuator is a pneumatic actuator. A control valve pneumatically coupled to the first linear actuator controls a flow of compressed air to the linear actuator from an air compressor. 
     In one embodiment, the second linear actuator is a chain drive. The chain drive includes a chain trained around a drive cog and a driven cog and having a straight segment extending therebetween. The straight segment of the chain is coupled to the first track. A shaft extends from the drive cog. A handle on the shaft allows control. Rotation of the handle causes rotation of the drive cog, which causes linear movement of the straight segment. 
     In one embodiment, a cowl (e.g., debris shield) is provided above the saw blade. The cowl includes a vacuum port coupled to a vacuum hose coupled to a vacuum for dust collection. A shield vertically movable relative to the cowl under the influence of contact with the walkway guards against propelled debris and helps to constrain dust from cutting. 
     While an exemplary embodiment of the invention has been described, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention. With respect to the above description then, it is to be realized that the optimum relationships for the components and steps of the invention, including variations in order, form, content, function and manner of operation, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. The above description and drawings are illustrative of modifications that can be made without departing from the present invention, the scope of which is to be limited only by the following claims. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents are intended to fall within the scope of the invention as claimed.