Patent Publication Number: US-8522803-B2

Title: Material-removal system

Description:
FIELD 
     The present disclosure relates to material-removal systems and, more particularly, to material-removal systems that include a fluid-blasting, spray-head assembly. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Material-removal systems can use a fluid-blasting, spray-head assembly (hereinafter referred to as “spray-head assembly”) to remove material from a surface. The spray-head assembly can direct a stream of high-pressure fluid onto a surface to remove material therefrom. 
     The spray-head assembly typically includes individual fluid bars that each rotate about an associated pivot. Each fluid bar is spaced apart and disposed within separate shrouds or housings and rotates therein. The shroud is open on one side to allow the pressurized fluid from the fluid bar to be directed toward the working surface. Each rotating fluid bar has an effective area or sweep over which the pressurized fluid is directed. The rotation of the fluid bar results in a circular sweep with a diameter that is related to the length of the fluid bar and the distance from the surface. To increase the effective area of the spray-head assembly, the multiple fluid bars are arranged so that the sweep of the individual rotating fluid bars overlaps one another as the spray-head assembly is moved over the surface. The use of individual or separate shrouds for each fluid bar, however, can result in a large spray-head assembly. The larger the spray-head assembly is, the more difficult it can be to control the spray-head assembly and/or maneuver the spray-head assembly into confined spaces or restricted areas. Thus, it would be advantageous to provide a spray-head assembly that allows for overlapping sweeps of the spray patterns while reducing the overall size of the spray-head assembly. 
     SUMMARY 
     The present disclosure teaches a fluid-blasting, spray-head assembly that can be used to remove coatings from a surface. The fluid-blasting head can include a plurality of fluid bars that each directs a flow of pressurized fluid at a desired surface. The fluid bars can rotate about individual pivots. The fluid bars can be indexed relative to one another such that the rotation of the fluid bars is coordinated. Multiple fluid bars can be disposed within a single shroud and can have overlapping sweeps such that a sweep of one of the rotating fluid bars can overlap the sweep of one or more adjacent rotating fluid bars. The fluid bars can be aligned in a straight configuration with overlapping sweeps. A gear assembly can be coupled to each of the fluid bars to index the rotation. A drive system can drive rotation of the fluid bars. A vacuum source can be connected to the shroud to capture debris and discharged fluid. 
     The spray-head assembly can include a plurality of fluid bars operable to direct a flow of high-pressure fluid toward a surface. The fluid bars can be simultaneously rotatable about individual axes and can overlap one another during rotation. A drive mechanism can drive rotation of the fluid bars about the respective axes. The drive mechanism can coordinate the rotation of the fluid bars such the fluid bars do not hit during the simultaneous rotation. The overlapping of the fluid bars can advantageously provide a spray-head assembly of reduced size. The fluid bars can be enclosed within a single cavity with a shroud. A vacuum source can be coupled to the spray-head assembly to capture discharge fluid and debris generated by the fluid in a debris tank. The vacuum source can draw a flow of cooling air over the drive mechanism to cool the drive mechanism. The drive mechanism can include a plurality of fins on the exterior thereof to facilitate the removal of heat with the cooling air flow. The captured discharge fluid can be filtered and reused to supply pressurized fluid to the spray-head assembly. 
     The spray-head assembly can be mounted on a device or mechanism operable to move the spray-head assembly along a surface from which material is to be removed. The mechanism or device can include a robotic mechanism, a cable driven system, and a self-propelled system. The surface can be horizontal, vertical, inclined, flat, curved, undulating, irregular and the like. The device or mechanism can be mobile to allow the spray-head assembly to move along a larger surface. The mobile mechanism can be a mobile platform that travels along the surface. The mobile platform can include a high-pressure fluid supply system operable to supply high-pressure fluid to the spray-head assembly. A fluid-storage tank and the debris tank can be coupled to or separate from the mobile platform. 
     A recirculation system can be used with the spray-head assembly. The recirculation system can capture fluid discharged by the spray-head assembly, filter the captured fluid and reuse the filtered fluid to supply a pressurized fluid flow to the spray-head assembly. 
     A peristaltic pump can communicate with a debris tank. The peristaltic pump can advantageously allow the removal of fluid from the debris tank while a vacuum system is creating a vacuum within the debris tank. 
     The fluid flow supplied to the spray-head assembly can be heated. The heated fluid flow can advantageously allow use of the spray-head assembly in lower temperature environments. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a side elevation view of an exemplary mobile platform having a material-removal system according to the present teachings; 
         FIG. 2  is a schematic representation of a water system that can be utilized in the material-removal system of  FIG. 1 ; 
         FIG. 3  is a schematic representation of a vacuum system that can be utilized in the material-removal system of  FIG. 1 ; 
         FIG. 4  is a schematic of a hydraulic system that can be utilized in the material-removal system of  FIG. 1 ; 
         FIGS. 5A  and B are fragmented side elevation views of the material-removal system of  FIG. 1  showing the debris tank in an operational and a dumping position, respectively; 
         FIG. 6A  is an end elevation view of the debris tank with the rear door removed; 
         FIG. 6B  is a cross-sectional view of the debris tank along line  6 B- 6 B of  FIG. 5A ; 
         FIGS. 7A  and B are fragmented perspective views of the articulating-arm assembly and spray-head assembly of the material-removal system of  FIG. 1  in an operational and non-operational position, respectively; 
         FIG. 8  is a perspective view of an exemplary spray-head assembly according to the present teachings; 
         FIG. 9  is a partial exploded view of portions of the spray-head assembly of  FIG. 8 ; 
         FIG. 10  is a bottom plan view of the spray-head assembly of  FIG. 8 ; 
         FIGS. 11A  and B are perspective views of the gear-box assembly utilized in the spray-head assembly of  FIG. 8 ; 
         FIG. 12  is a cross-sectional view along line  12 - 12  of  FIG. 11A ; 
         FIG. 13  is an enlarged fragmented view of the center fluid bar portion of the gear box assembly of  FIG. 12 ; 
         FIG. 14  is a partially-cutaway perspective view of the lower shell of the gear-box assembly of  FIG. 11 ; 
         FIG. 15  is an exploded view of the gear box assembly of  FIG. 11 ; 
         FIG. 16  is a schematic representation of another exemplary spray-head assembly according to the present teachings; 
         FIG. 17  is a schematic representation of a suspension system that can be utilized on the mobile platform containing the material-removal system according to the present teachings; 
         FIG. 18  is a schematic representation of an exemplary recirculation system that can be utilized with a spray-head assembly according to the present teachings; 
         FIG. 19  is a schematic representation of an exemplary heated fluid supply system that can be utilized with a spray-head assembly according to the present teachings; 
         FIG. 20  is a representation of a spray-head assembly according to the present teachings removing material from a side of a ship; 
         FIG. 21  is a representation of a spray-head assembly according to the present teachings removing material from an exterior of a water tower; and 
         FIG. 22  is a fragmented representation of a spray-head assembly according to the present teachings removing material from a bridge member. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     Referring to  FIG. 1 , a material-removal system  20  according to the present teachings is disposed on a mobile platform  22 , such as a vehicle or truck. In the figures, mobile platform  22  is shown as a six-axle truck having a cab  24  and a frame  26 . It should be appreciated that mobile platform  22  can take other forms. For example, mobile platform  22  can be a movable robotic mechanism, a cable system and other moveable devices and mechanisms. Material-removal system  20  can include a fluid-blasting, spray-head assembly  28  which can be coupled to vehicle  22  with an articulating-arm assembly  30 . Spray-head assembly  28  can direct high-pressure fluid at a surface to remove debris therefrom, as described below. Material-removal system  20  can include a fluid-supply system  32  which can supply high-pressure fluid to spray-head assembly  28 . Fluid-supply system  32  can be disposed on vehicle  22 . Material-removal system  20  can also include a vacuum system  34  that can supply a vacuum to spray-head assembly  28 . The vacuum can suck up the fluid discharged by spray-head assembly  28  and the debris generated thereby and deposit same in a debris tank  36 , as described below. Vacuum system  34  can be disposed on vehicle  22 . 
     Referring now to  FIGS. 1 and 2 , details of fluid-supply system  32  are shown. Fluid-supply system  32  can include a storage tank  40  that supplies a fluid therein to a high-pressure pump  42 . Storage tank  40  can have an external sight gage  41  to allow visual ascertation of the liquid level therein. High-pressure pump  42  is operable to supply high-pressure fluid, such as water, at a high pressure, such as 40,000 PSI + or −, to spray-head assembly  28  through a high-pressure fluid line  44 . High-pressure pump  42  can supply high-pressure fluid to spray-head assembly  28  at a rate of about 0-24 gpm + or −. A suitable high-pressure pump  42  can take a variety of forms. One suitable pump includes Jet Stream Model No. 4200 available from Jet Stream of Houston, Tex. A charge pump  46  can be used to supply fluid from storage tank  40  to high-pressure pump  42 . A filter  48  can filter the fluid flowing from charge pump  46  to high-pressure pump  42 . Optionally, charge pump  46  can also supply a flow of cooling fluid to spray-head assembly  28 , via an optional cooling line  50 . High-pressure pump  42  can be driven by an auxiliary engine  52  mounted on vehicle  22 . For example, auxiliary engine  52  can drive high-pressure pump  42  with a belt-and-pulley system. Auxiliary engine  52  can be a diesel engine. A PTO from the vehicle engine can also be used. 
     Referring now to  FIGS. 1 and 3 , details of vacuum system  34  are shown. Vacuum system  34  can include a vacuum pump  60  that communicates with debris tank  36 . Pump  60  can pull a vacuum on debris tank  36  to facilitate the collection of debris and liquid waste therein. Debris tank  36  communicates with spray-head assembly  28  through a vacuum hose  62 . The vacuum created in debris tank  36  allows spray-head assembly  28  to suck in debris, air, and waste liquid and deposit the debris and waste liquid in debris tank  36  via vacuum hose  62 . Debris tank  36  can communicate with one or more centrifugal filters  64  with a vacuum line  65 . Centrifugal filters  64  and a media filter  66  can be utilized to remove particles in the air flowing from debris tank  36  to vacuum pump  60 . Vacuum pump  60  can discharge the air to the environment through a muffler  68 . Vacuum pump  60  can be driven by a hydraulic motor  70 . Vacuum system  34  can pull a vacuum of about 10-16″ Hg to facilitate the capturing of debris and waste liquid in debris tank  36 . Suitable vacuum pumps include those available from Kaeser Compressors, Inc. of Fredricksburg, Va. 
     In operation, debris, liquid, and air are sucked into spray-head assembly  28  and flow through hose  62  and dump into debris tank  36 . The air flows out of debris tank  36  and into centrifugal filter(s)  64  and subsequently into a media filter  66 . The air leaves media filter  66  and flows through vacuum pump  60  and is discharged to the environment through muffler  68 . Vacuum system  34  can also induce a flow of cooling air through spray-head assembly  28  that can flow across a gear box therein, as described below. 
     Referring now to  FIGS. 1 and 4 , details of a hydraulic system  80  that can be utilized in material-removal system  20  and on vehicle  22  is shown. Hydraulic system  80  can include a hydraulic fluid tank  82  that can supply hydraulic fluid to hydraulic pumps  84 , such as pump  84   a ,  84   b , and  84   c . Each hydraulic pump  84  can drive an associated hydraulic motor  86 , such as hydraulic motors  86   a ,  86   b , and  86   c . Hydraulic pumps  84  can be driven by auxiliary engine  52  or by the main vehicle engine  88 . The number of hydraulic pumps  84  and associated hydraulic motors  86  will vary depending upon the needs of material-removal system  20  and vehicle  22 . Additionally, which hydraulic pumps  84  are driven by auxiliary engine  52  and which are driven by vehicle engine  88  will also vary depending upon the power needs of the particular hydraulic pump and/or its location on vehicle  22 . For example, hydraulic pump  84   a  and motor  86   a  can be associated with spray-head assembly  28  while hydraulic pump  84   b  and hydraulic motor  86   b  can be associated with the hydrostatic drive of vehicle  22 , and hydraulic pump  84   c  and hydraulic motor  86 , can be associated with articulating-arm assembly  30 . It should be appreciated that the description of hydraulic pumps  84  and associated motors  86  is merely exemplary in nature and that the particular components of material-removal system  20  and mobile platform  22  will vary depending upon the design. 
     Referring now to  FIG. 5 , details of debris tank  36  are shown. Debris tank  36  includes a rear door  90  that pivots about an upper hinge  92 . Door  90  can pivot between a closed position, as shown in  FIG. 5A , to an open position, such as that shown in  FIG. 5B . Door  90  can include one or more seals (not shown) to seal door  90  to debris tank  36  when closed and facilitate forming a vacuum therein. An extendible actuator  94 , such as a hydraulic cylinder, can move between a retracted position, as shown in  FIG. 5A , and an extended position, as shown in  FIG. 5B , to open and close door  90 . Another extendible actuator  96 , such as a hydraulic cylinder, can move between an extended position, as shown in  FIG. 5A , and a retracted position, such as that shown in  FIG. 5B , to engage and disengage a locking arm  98  from a locking pin  100  on door  90 . Debris tank  36  can be pivoted about a hinge  106  between an operational position, such as shown in  FIG. 5A , and a dumping position, such as that shown in  FIG. 5B . An actuator  108 , such as a telescopic hydraulic arm, can be extended and retracted to move debris tank  36  between the positions shown in  FIGS. 5A and 5B . Vacuum lines  62 ,  65  can each have a separable compression sealable joint  110  that allows lines  62 ,  65  to be separated during the movement of debris tank  36 . 
     Referring now to  FIGS. 6A  and B, details of the internal configuration of debris tank  36  are shown. Debris tank  36  can have straight walls interconnected with curved corners. Alternatively, debris tank  36  can be more cylindrical in cross-section. Along the top surface of debris tank  36  is a float-check device  118  that includes a float  120  within a cage  122 . Float  120  can be generally conical in shape and can include a tapering surface  123 . Float  120  can float and will rise with the liquid level in debris tank  36 . Float  120  can be bottom weighted to maintain the orientation shown within cage  122 . As float  120  rises, tapering surface  123  can gradually restrict port  125  to restrict flow through vacuum line  65  (which is connected to port  125 ) as the liquid level increases. Float  120  can block port  125  when the liquid level is high enough. Thus, as the liquid level in debris tank  36  rises, float  120  can rise and restrict and/or plug port  125  thereby gradually restricting port  125  and preventing liquid from being sucked into vacuum pump  60 . 
     Debris tank  36  includes an inlet port  124  through which debris, liquid, and air sucked up by spray-head assembly  28  can be received into the interior of debris tank  36 . Vacuum hose  62  can be coupled to inlet  124 . Debris tank  36  can include a sight window  126 , as shown in  FIGS. 1 and 5 , which allows the liquid level within debris tank  36  to be visually ascertained. Debris tank  36  can include a filtration cage  128  that facilitates the separation of the liquid from the debris therein when draining the liquid from debris tank  36 . Filtration cage  128  can include three vertically-extending walls  130  and a horizontal wall  132 . The walls  130 ,  132  of filtration cage  128  are spaced inwardly apart from the vertically-extending side walls and horizontal bottom wall of debris tank  36 . The top edges  131  and the rear edges  133  of walls  130  are sealed to the side walls and front walls of debris tank  36 . A rear edge  135  of wall  132  is not sealed to the bottom wall of debris tank  36 . 
     A space  134 , as shown in  FIG. 6B , thereby exists between the walls of debris tank  36  and walls  130 ,  132  of gage  128 . The seal(s) on door  90  can seal against rear edges  133 ,  135  of walls  130 , 132  to prevent liquid and debris from passing therebetween and into space  134  without flowing through the perforations in walls  130 ,  132 . The seal(s) on door  90  also seal against the rear edges of the walls of debris tank  36 , as stated above. Walls  130 ,  132  are perforated to allow liquid to be drawn, with suction, therethrough. The perforations allow the liquid to be drawn therethrough while preventing debris larger than the size of the perforations from passing beyond filtration cage  128 . Filtration media (not shown) can be affixed to walls  130 ,  132  to provide a greater level of filtration than possible with just perforated walls  130 ,  132 . The filtration media can be sized to filter down to a desired particle size while allowing the liquid to be drawn therethrough and past walls  130 ,  132  through the perforations therein. 
     Debris tank  36  can include a plurality of openings in the bottom thereof to allow the removal of the liquid therefrom. A pair of discharge pipes  136  with valves  138  therein can be coupled to the ports on the bottom of debris tank  36 . Valves  138  can be selectively opened to allow the liquid within debris tank  36  to be drained therefrom. During operation, valves  38  can be closed and debris tank  36  under vacuum by vacuum system  34 . When material-removal system  20  is idle (i.e., vacuum system is not running), valves  138  can be opened to allow the liquid within space  134  to be drained therefrom. 
     In some applications, it may be necessary or desirable to remove liquid or liquid and debris from debris tank  36  during operation of material-removal system  20  (i.e., such as when vacuum system  34  is operational and debris tank  36  is under vacuum). Such possibilities may occur when it is permissible to discharge the liquid and/or debris captured within debris tank  36  directly to the environment. For this type of operation, however, debris tank  36  is under vacuum and removal from debris tank  36  can be difficult. The inventor has advantageously discovered that a peristaltic pump  140  can be utilized to remove liquid and debris from debris tank  36  during operation of material-removal system  20  and vacuum system  34 . Peristaltic pump  140  can be coupled to one of the discharge valves  138  with a flexible hose  142 . The associated valve  138  can be opened and peristaltic pump  140  can be operated to draw liquid and, if desired, debris from debris tank  36  while vacuum system  34  is operational thereby allowing debris tank  36  to remain under vacuum. Peristaltic pump  140  can discharge the liquid and debris removed from debris tank  36  to the environment through an outlet  144 . Peristaltic pump  140  can be hydraulically driven. Suitable peristaltic pumps include Allweiler pumps available from Imo Pump of Monroe, N.C. 
     Removing liquid from debris tank  36  while traveling down the road can advantageously reduce down time and the time needed to recharge material removal system  20 . Thus, in the event that the quantity of debris within debris tank  36  does not necessitate that the debris be physically removed from debris tank  36 , when vehicle  22  arrives at a servicing station for service, it may be possible to only require the filling of fluid-storage tank  40  to enable further operation of material-removal system  20 . That is, fluid-storage tank  40  can be filled at a much quicker rate than the waste fluid can be removed from debris tank  36 . Thus, by removing the fluid from debris tank  36  while traveling down the road with peristaltic pump  140 , the servicing time required to service material-removal system  20  can be significantly reduced thereby providing increased up time and greater revenue generation from material-removal system  20 . Additionally, the pumping of liquid from debris tank  36  can draw the fluid through the filtration media affixed to walls  130 ,  132 . Liquid can also be removed from debris tank  36  during the dumping operation. That is, when debris tank  36  is tilted upwardly, the liquid along with the debris therein can be removed by opening door  90 . A suitable debris tank can be acquired from Flo Trend Systems of Houston, Tex. For example, Flo Trend Model No. VM-08-G/V debris tank can be utilized in material-removal system  20 . 
     Referring now to  FIGS. 7A  and B, details of articulating-arm assembly  30  are shown. Articulating-arm assembly  30  can be a four-bar mechanism  160  having a base plate  162  and a spray-head plate  164 . One end of a pair of upper arms  166  is pivotally coupled to base plate  162  while the other end of a pair of upper arms  166  is pivotally coupled to spray-head plate  164 . Similarly, one end of a pair of lower arms  168  is pivotally coupled to a lower position on base plate  162  while the other end of a pair of lower arms  168  is pivotally coupled to a lower position on spray-head plate  164 . Thus, base plate  162 , upper arms  166 , spray-head plate  164 , and lower arms  168  form a four-bar mechanism that enables spray-head assembly  28  to be moved from an operational position, such as shown in  FIG. 7A , to a non-operational position, such as that shown in  FIG. 7B . To move four-bar mechanism  160  between the operational and non-operational positions, an extendible actuator  170 , such as a hydraulic cylinder, can have one end coupled to base plate  162  while an opposite end of actuator  170  can be coupled to spray-head plate  164 . Extension and retraction of actuator  170  can thereby move the four-bar mechanism and spray-head assembly  28  between the operational position and non-operational position. 
     Articulating-arm assembly  30  can also include a rotary actuator  174 , such as a hydraulic actuator, that pivotally couples base plate  162  to the front bumper of vehicle  22 . Rotary actuator  174  can rotate articulating-arm assembly  30  along about a vertically-extending axis. Articulating-arm assembly  30  can also include another rotary actuator  176 , such as a hydraulic actuator, that can pivotally couple spray-head plate  164  to spray-head assembly  28 . Rotary actuator  176  can thereby pivot spray-head assembly  28  relative to articulating-arm assembly  30  about a vertical axis. 
     Referring now to  FIGS. 8-11 , details of spray-head assembly  28  are shown. Spray-head assembly  28  includes a base plate  180  to which a gear-box assembly  182  is attached. Rotary actuator  176  of articulating-arm assembly  30  can be attached to base plate  180 . Gear-box assembly  182  can include a plurality of shafts  184  that extend therethrough. Fluid bars  186  can be coupled to the ends of shafts  184  and used to direct pressurized fluid onto a surface to remove material therefrom, as described below. A shroud  190  can be attached to base plate  180  and form an enclosure for fluid bars  186 . A flexible skirt  194  can be attached to shroud  190  and skim along the surface upon which spray-head assembly  28  is traveling. A plurality of wheels  198  can be coupled to base plate  180  and/or shroud. Wheels  198  can ride along the road or surface upon which spray-head assembly  28  is being utilized and can maintain spray-head assembly  28  a predetermined distance from the surface. 
     Gear-box assembly  182  can be driven by a hydraulic motor  210  to rotate fluid bars  186 , as described below. Motor  210  can be mounted to gear-box assembly  182 . Vacuum hose  62  is split and coupled to base plate  180  at multiple locations. In the material-removal system  20  shown, vacuum hose  62  is split into two lines  62   a ,  62   b  and can pass through openings  212 ,  214  in base plate  180  and be coupled to two vacuum ports  216 ,  218  on shroud. The attachment of vacuum hose  62  at these multiple locations facilitates the capture of the debris removed from the surface along with the fluid expelled by fluid bars  186 , as described below. Additionally, the suction imparted on the cavity of shroud  190  facilitates the drawing of cooling air over gear-box assembly  182 . Specifically, base plate  180  can have a plurality of ventilation openings  220  that align with a plurality of ventilation openings  222  in shroud  190 . When vacuum hose  62  is sucking a vacuum on the cavity formed by shroud  190 , along with air that enters cavity around skirt  194 , air can also enter the cavity through ventilation openings  220 ,  222 . The air entering ventilation openings  220 ,  222  passes between base plate  180  and gear-box assembly  182  thereby providing a flow of cooling or ventilating air across the surface of gear-box assembly  182 . Ventilation openings  220 ,  222  can be disposed beneath gear-box assembly  182  at desired positions to encourage a desirable flow pattern across the surface of gear-box assembly  182 . It should be appreciated that the location, size, and number of ventilation openings  220 ,  222  can vary depending upon the cooling needs of spray-head assembly  28  and gear-box assembly  182 . High-pressure fluid line  44  is coupled to spray-head assembly  28  and communicates with each shaft  184  to supply high-pressure fluid to the associated fluid bar  186 , as described below. 
     Referring now to  FIG. 10 , the bottom side of spray-head assembly  28  is shown. Each fluid bar  186  rotates along with rotation of shaft  184 . As a result, each fluid bar  186  has a sweep area defined by broken line  230 . The sweep area  230  of each fluid bar  186  can overlap the sweep area  230  of one or more other fluid bars  186 , depending upon the arrangement of fluid bars  186  and shafts  184 . As shown, fluid bars  186  can be arranged in a straight line and can be coplanar with one another. If desired, however, fluid bars  186  can be arranged in a non-linear configuration with or without overlapping sweep areas  230 , and coplanar or non-coplanar, although all of the advantages may not be realized. With sweep areas  230  overlapping, the rotation of fluid bars  186  about their respective axis is coordinated to prevent fluid bars  186  from hitting or interfering with one another, as described below. 
     The sweep area  230  of each fluid bar  186  is representative of the area over which the associated fluid bar  186  can direct high-pressure fluid. The overlap of sweep areas  230  results in overlapping regions  234 . Overlapping regions  234  allow for redundant coverage of the surface over which spray-head assembly  28  travels. Overlapping regions  234  may allow for quicker removal of the material or coating from the surface and may increase the rate at which vehicle  22  can be operated. Overlapping regions  234  may increase the efficiency of the removal operation and may reduce the costs associated with the removal. Additionally, the use of overlapping regions  234  can reduce the overall size of spray-head assembly  28  thereby facilitating the movement of spray-head assembly  28  over or into confined or restricted spaces. Additionally, articulating-arm assembly  30  can be adjusted and/or spray-head assembly  28  rotated, as described above, to change the spray pattern imparted upon the surface over which spray-head assembly  28  travels to accommodate wider or narrower areas of coverage of the surface. 
     Referring now to  FIGS. 11-15 , details of gear-box assembly  182  and fluid bars  186  are shown. Gear-box assembly  182  can include upper and lower housings  250 ,  252  that are secured together. Upper housing  250  can include a plurality of spray-shaft openings  254  and a drive opening  256 . Lower housing  252  can include a plurality of spray-shaft openings  258  that are aligned with openings  254  of upper housing  250 . Lower housing  252  does not include a drive opening therein as the shaft used to drive gear-box assembly  182  does not need to extend outwardly beyond lower housing  252 . Lower housing  252  can include a plurality of fins  260  that extend therefrom. Fins  260  can facilitate the removal of heat from gear-box assembly  182 . During operation of spray-head assembly  28 , the suction caused by vacuum system  34  can draw air through ventilation openings  220 ,  222  in base plate  180  and shroud  190 . The air can flow over fins  260  on its way to vacuum ports  216 ,  218 . Thus, vacuum system  34  can facilitate the drawing of cooling air over fins  260  of gear-box assembly  182 . Additional cooling can be provided through the use of an internal flow channel  264  in lower housing  252  (best seen in  FIGS. 12 and 14 ). Flow channel  264  can extend along the periphery of lower housing  252  and can communicate with input and output channels  266 ,  268 . Input channel  266  can be coupled to the optical cooling line  50  ( FIG. 2 ) to supply a flow of cooling liquid through flow channel  264 . The liquid can exit output channel  268  to be recovered by vacuum system  34 . If desired, input and output channels  266 ,  268  can be coupled to the cooling system for vehicle engine  88  to provide a closed-loop cooling system to facilitate the removal of heat from gear-box assembly  182 . Furthermore, the size, shape, and orientation of cooling fins  260  can vary from that shown to facilitate heat transfer and/or manufacture. Optionally, upper housing  250  can also be provided with fins (not shown) to facilitate the cooling of gear-box assembly  182 , if desired. 
     Upper housing  252  can include grease channels  272  that communicate with spray openings  254  and drive opening  256 . Grease channels  272  allow grease to be inserted into the bearings of gear-box assembly  182 . Lower housing  252  can also include a grease channel (not shown) that allows grease to be inserted into a lower drive gear bearing of gear-box assembly  182 . 
     Gear-box assembly  182  provides an indexing feature wherein the rotation of fluid bars  186  about their rotation axis is coordinated. The indexing feature prevents the rotation of fluid bars  186  from interfering with one another. The indexing feature of gear-box assembly  182  is provided through the intermeshing of gears associated with each fluid bar  186  and its associated shaft  184 . As best seen in  FIGS. 12 and 15 , gear-box assembly  182  includes shafts  184  for each fluid bar  186 . In the embodiment shown, three shafts  184  and three fluid bars  186  are utilized. It should be appreciated, however, that gear-box assembly  182  can be configured for as few as two shafts or more than three shafts, as desired. Each shaft  184  includes an upper portion  280  that extends upwardly out of upper housing  250 . Upper portion  280  is configured to be attached to a fluid coupler that communicates with high-pressure fluid line  44 . Each shaft  184  has a lower portion  282  that is received within a fluid bar  186  and communicates with the flow channels therein. A flow channel  284  extends between upper and lower portions  280 ,  282  of each shaft  184 . Channel  284  allows high-pressure fluid to be supplied to fluid bars  186  through shafts  184 . Each shaft  184  can also include first and second sets of teeth  286 ,  288  on an intermediate portion thereof. First set of teeth  286  engages with a coupler  292  that couples shaft  184  to an associated fluid bar  186 . Coupler  292  includes an internal bore having teeth  294  therein. Teeth  294  engage with teeth  286  to rotationally fix coupler  292  to shaft  184 . Coupler  292  can include a recessed channel  296  that can engage with opposing flats  298  on fluid bars  186 . The engagement of channel  296  with flats  298  rotationally locks the fluid bar  186  to coupler  292  and, therefore, to the associated shaft  184 . 
     Shafts  184  are disposed within gear-box assembly  182  with upper and lower portions  280 ,  282  extending outwardly beyond the respective upper and lower housings  250 ,  252 . Each shaft  184  can be disposed within a channel extending through a hub  300  of a gear  302 . Second set of teeth  288  can engage with a set of teeth within the channel of hub  300 . The engagement of these teeth can rotationally lock shaft  184  to an associated gear  302 . An upper bushing  304  can be disposed around the upper portion of the hub  300  and can engage with a shoulder of a spray opening  254  of upper housing  250 . An upper bearing  306  can be disposed around the upper portion of hub  300  between bushing  304  and hub  300 . Bushing  304  can include a fluid channel that communicates with the grease channel  272  in upper housing  250  to allow grease to be supplied to upper bearing  306 . A lower bushing  307  can be disposed around the lower portion of the hub  300  and can engage with a shoulder of a spray opening  258 . A lower bearing  308  can be disposed around the lower portion of hub  300  between bushing  307  and hub  300 . Bushing  307  can include a fluid channel to allow grease to be supplied to lower bearing  308 . The lower portion of hub  300  can extend through a plate  312  which can be secured to lower housing  252  coaxial with an associated spray opening  258 . Plate  312  can include a grease channel  314  that allows grease to be supplied to lower bearing  308  through bushing  307 . Shaft  184  is thereby axially constrained relative to upper and lower housings  250 ,  252 . A shield  316  can be disposed on coupler  292  around shaft  184 . Shield  316  can inhibit the flow of debris and blasting fluid from flowing upwardly and contacting plate  312  and the lower portion of hub  300 . 
     Gears  302  have a set of teeth  318  that are intermeshed with one another. The intermeshing of teeth  318  of each gear  302  with another gear  302  rotationally links each shaft  184  and an associated fluid bar  186  with the other shafts  184  and fluid bars  186 . As a result, the rotation of shafts  184  and the associated fluid bars  186  are coordinated so that fluid bars  186  do not interfere with or crash into one another during rotation. 
     Gear-box assembly  182  can also include a drive gear  330  with a set of teeth  332  thereon. Teeth  332  of drive gear  330  are intermeshed with teeth  318  in an adjacent gear  302 . Rotation of drive gear  330  is translated into rotation of gears  302  through the intermeshing of the associated teeth  332 ,  318 . Drive gear  380  includes a hub  333  with a set of internal teeth  336  therein. Teeth  336  can engage with the splines on a driveshaft of hydraulic-drive motor  210  to drive spray-head assembly  28 . Optionally, a shear gear or coupler (not shown) can be disposed between the driveshaft of motor  210  and teeth  336  and can operate as a sacrificial part in the event of an overload condition, such as one of the fluid bars hitting an object. A bushing  338  can extend around the upper portion of hub  333  and can engage with a side wall of drive opening  256  of upper housing  250 . An upper bearing  340  can be disposed between the upper portion of hub  333  and bushing  338 . A lower bearing  342  can engage with a drive recess  334  in lower housing  252  which is arranged coaxially with drive opening  256  in upper housing  250 . An upper plate  346  can be attached to the exterior surface of upper housing  250  coaxial with drive opening  256 . Plate  346  can engage with bushing  338  to retain drive gear  330  between upper and lower housings  250 ,  252 . Bushing  338  can include a channel that communicates with the grease channel  272  associated with drive opening  256  to facilitate the addition of grease to upper bearing  340 . Similarly, lower housing  252  can include a grease channel (not shown) that facilitates the addition of grease to lower bearing  342 . 
     Gear-box assembly  182  can be filled with an oil, such as a synthetic oil, to lubricate gears  302 ,  330  and their relative rotation. Lower housing  252  can include an input port  350  and an output port  352  that can, respectively, be used to add oil to and remove oil from gear-box assembly  182 . Upper housing  250  can include a breather hole  354 . 
     As best seen in  FIG. 13 , fluid bars  186  can be rectangular in cross section. Fluid bars  186  can include a generally-horizontally-extending flow channel  380  that communicates with flow channel  284  in the associated shaft  184 . Fluid bars  186  can include a plurality of spray channels  382  that extend downwardly from flow channel  380 . Spray channels  382  extend from flow channels  380  to nozzle cavities  384 . Nozzle cavities  384  can receive a nozzle therein. The nozzles (not shown) can take a variety of forms and can provide a variety of spray patterns, as desired. The particular spray pattern chosen will depend upon the material to be removed and the surface upon which material-removal system  20  is operating. Fluid bars  186  can also include horizontally-extending nozzle cavities  386  on the ends of flow channels  380 . The end nozzle cavities  386  can provide a fluid spray that helps clean the shroud of debris, if desired. Nozzle cavities  384 ,  386  can be plugged so that those nozzle cavities are not utilized to provide a fluid flow to remove material from the surface. 
     Spray channels  382  and the associated nozzle cavities  384  can be angled relative to the axis of rotation of shaft  184 . For example, as shown in  FIG. 13 , spray channels  382  and nozzle cavities  384  can be angled outwardly as they extend downwardly. As a result, the spray pattern imparted upon the surface may provide an incident angle that is less than 90 degrees. By having the spray pattern hit the surface at a non-orthogonal angle, the fluid flow can facilitate the removal of material from the surface. For example, the glancing nature of the spray pattern can help lift the material from the surface. Spray channels  382  and nozzle cavities  384  can all have the same angular offset from the rotation axis or can vary from one another. Additionally, it should be appreciated that spray channels  382  and nozzle cavities  384  can also vary angularly into and out of the page in the view depicted in  FIG. 13 . That is, some of spray channels  382  and nozzle cavities  384  can be angled out of the page and some into the page in the view depicted in  FIG. 13 . Thus, as high-pressure fluid is supplied to fluid bars  186  and fluid bars rotate with the rotation of shafts  184 , the high-pressure fluid can be directed to the surface at a glancing angle and the spray pattern rotated along the surface. The movement of spray-head assembly  28  along the surface directs the spray pattern along the surface and the removal of the material therefrom is facilitated. 
     Referring now to  FIG. 10 , the rotation of each fluid bar  184  is opposite that of the adjacent fluid bar. The intermeshing of gears  302  results in this opposite rotation. For example, as shown in  FIG. 10 , the two outermost fluid bars  186  can rotate counterclockwise while the center fluid bar  186  rotates clockwise. This opposite rotation of the adjacent fluid bars can advantageously direct the material removed from the surface toward a particular portion or portions of spray-head assembly  28 . The vacuum ports  216 ,  218  can be advantageously provided on spray-head assembly  28  to coincide with the general area to which the debris is directed due to the relative rotations of fluid bars  186 . For example, as shown in  FIG. 10 , the material removed from the surface can be directed toward one of the side walls of shroud  190 , as indicated by arrows  392 . In this embodiment, the debris is directed toward the front and back sides of shroud  190 . Vacuum ports  216 ,  218  can be disposed in the area wherein debris arrows  392  converge to facilitate the capturing of the debris with the suction and the deposit in debris tank  36 . Thus, the different relative rotations of fluid bars  186  can be utilized to direct the debris toward strategically-placed vacuum ports  216 ,  218 . It should be appreciated, however, that the gearing can be arranged such that the fluid bars all rotate in a same direction, if desired. 
     Referring now to  FIG. 17 , a simplified representation of the suspension system  400  for vehicle  22  is shown. Suspension system  400  can transfer the loading on each of the axles so that a similar load is seen by each axle. The ability to shift the loading can be advantageous in that during operation of vehicle  22  and material-removal system  20 , the load on vehicle  22  varies. That is, as the fluid within fluid-storage tank  40  flows through spray-head assembly  28 , and is recovered and sucked into debris tank  36 , the loading on the various axles will change. By equalizing the loading, more stable operation of vehicle  22  can be achieved along with the provision of not overloading any particular axle. Suspension system  400  can include a plurality of equalizer beams  402  connected between adjacent leaf-spring assemblies for adjacent axles. Suspension systems having such load-transferring capabilities are disclosed in U.S. Pat. No. 5,234,067, entitled “Tandem Axle Suspension for Vehicle,” by Simard; U.S. Pat. No. 6,604,756, entitled “Tridem Axle Suspension,” by Simard; and U.S. Pat. No. 6,382,659, entitled “Load Distributing Tandem Suspension Assembly,” by Simard, the disclosures of which are incorporated herein by reference. 
     Referring now to  FIG. 16 , an alternate spray-head assembly  28 ′ using a different drive system is shown. In this drive system, hydraulic motor  210 ′ has an output shaft  412 ′ that can have a sheave  414 ′ thereon. A driveshaft  416 ′ can be engaged with drive gear  330 ′. Driveshaft  416 ′ can have a sheave  418 ′ thereon. A belt  420 ′ can interconnect sheaves  414 ′,  418 ′ to transfer rotation of output shaft  412 ′ to driveshaft  416 ′. Drive gear  330 ′ can engage with gears  302 ′ to drive rotation of fluid bars  186 ′. In this manner, motor  210 ′ can drive rotation of drive gear  330 ′ and operation of spray-head assembly  28 ′. Belt  420 ′ can function as the sacrificial component in the event that an overload condition occurs, such as when a fluid bar  186 ′ encounters an obstacle. 
     Referring now to  FIG. 18 , an exemplary recirculation system  520  for use with a spray-head assembly  522  is shown. Recirculation system  520  enables captured discharged fluid to be reused (recirculated) to supply pressurized fluid to spray-head assembly  522 . Recirculation system  520  takes captured discharge fluid from debris tank  524 , removes particulate matter therefrom and supplies the fluid to fluid supply tank  526  for subsequent supplying to spray-head assembly  522  with high-pressure fluid supply system  528 . High-pressure fluid supply system  528  can be similar to fluid-supply system  32  discussed above and shown in  FIG. 2 . Recirculation system  520  can include a pump  530  or other fluid displacement device that can draw captured discharge fluid from debris tank  524 , which may be under vacuum. One or more filtering devices  532  removes particulate matter from the fluid removed from debris tank  524 . The filtered fluid is routed to fluid supply tank  526  through line  534 . Optionally, the filtered fluid may be routed directly to high-pressure fluid supply system  528 , as indicated by fluid line  536  (shown in phantom). 
     The use of recirculation system  520  may allow the system using spray-head assembly  522  to operate for a longer continuous duration due to the increased quantity of fluid available to be supplied to spray-head assembly  522 . Specifically, for a given fluid supply tank  526 , if the captured discharged fluid is not recirculated the quantity of fluid that can be supplied to spray-head assembly  522  is limited to the capacity of fluid supply tank  526 . By using recirculation system  520 , the captured discharge fluid can be reused to increase the total quantity of fluid that can be supplied to spray-head assembly  522  without refilling. The increased duration can be effected by the efficiency of capturing discharged fluid and the ability to withdraw captured discharge fluid from debris tank  524 . The longer continuous duration can allow for more efficient material removal and less down time. 
     It should be appreciated that recirculation system  520  can include more or less components than shown and can be implemented in a variety of mechanizations. For example, recirculation system  520  can include a combination of pumps, separators, filters, chemical treatment devices, catalysts, electrical current devices, and mechanical devices, all of various types, arranged in series and/or parallel. Preferably, the recirculated fluid has sufficient particulate matter removed to not adversely affect the nozzle life or life of other components of the spray-head assembly. For example, it is preferred that the recirculated fluid not contain particulates in excess of about 1.0 microns. 
     Referring now to  FIG. 19 , an exemplary heated fluid supply system  620  for use with a spray-head assembly  622  is shown. Heated fluid supply system is operable to heat the high-pressure fluid supplied to spray-head assembly  622 . Heated fluid supply system can include a high-pressure fluid supply system  624 , which can be similar to fluid-supply system  32  discussed above and shown in  FIG. 2 , which draws fluid from a fluid supply tank  626 . The fluid supplied to spray-head assembly  622  flows through a heating device  628 , such as a heat exchanger, disposed between fluid supply tank  626  and high-pressure fluid supply system  624 . Within heating device  628 , heat is transferred to the fluid flowing therethrough and supplied to high-pressure fluid supply system  624  and spray-head assembly  622 . For example, when heating device is a heat exchanger, relatively hot heating fluid, such a hot coolant, can be routed through heat exchanger  628  in heat-conducting relation with the relatively cold blasting fluid being routed to spray-head assembly  622 . The heating fluid transfers heat to the blasting fluid thereby increasing the temperature of the blasting fluid. The heating of the blasting fluid can enable the use of high-pressure fluid supply system  624  and spray-head assembly  622  in a lower temperature environment than when used without heated blasting fluid. It should be appreciated that heating device  628  can take other forms than the heat exchanger shown. For example, an electric heating device may be used. Furthermore, it should be appreciated that it may be possible to dispose heating device  628  in a different location along the supply route between fluid supply tank  626  and spray-head assembly  622 . The use of heating device  628  can maintain the temperature of the blasting fluid (and the components through which the blasting fluid travels) above its freezing point and/or allow the temperature of the blasting fluid to be at a controlled temperature. 
     A spray-head assembly according to the present teachings can be used to remove material from a variety of hard surfaces. Such surfaces can be horizontal, vertical, inclined, flat, curved, undulating, irregular, and the like. The material being removed from the surface can include, but is not limited to, paint, coatings, graffiti and the like. Referring now to  FIGS. 20-22 , a spray head assembly  722  is shown being used to remove material from a ship  724 , a water tower  726 , and a bridge member  728 , respectively. Spray-head assembly  722  can be moved along the surface of ship  724 , water tower  726  and bridge member  728  by a driving mechanism  730 . Driving mechanism  730  can take a variety of forms. For example, driving mechanism  730  can be a robotic arm, a mobile robot, a cable driven system, a track along which spray-head assembly  722  travels and the like. The driving mechanism  730  can be fixed in place and move spray-head assembly  722  along the surface or can be mobile to increase the surface over which spray-head assembly  722  can travel. 
     While spray-head assembly  722  in  FIGS. 20-22  is shown as being used on exterior surfaces of ship  724 , water tower  726  and bridge  728 , it should be appreciated that a spray-head assembly according to the present teachings can be used on other surfaces. By way of non-limiting example, spray-head assemblies according to the present teachings can be used on interior surfaces, ceilings, walls, ship decks, roadways, floors, buildings and the like. 
     While the present invention has been described with reference to specific components, configurations, and arrangements, it should be appreciated that variations can be made to the embodiments disclosed without deviating from the teachings of the present invention. For example, while hydraulic-actuated cylinders, actuators, and motors shown as being used with material-removal system  20 , it should be appreciated that other types of actuators, such as electric, pneumatic, steam, and the like, can also be employed. Additionally, the number of vacuum ports and their arrangements can also vary from that shown. Moreover, the number of fluid bars utilizing each spray-head assembly and their orientation can also vary from that shown. Additionally, while the fluid bars  186  are shown as overlapping one another during rotation, fluid bars  186  can be spaced apart such that fluid bars  186  do not overlap one another (i.e., cannot hit one another) and still be coordinated (indexed) with gear-box assembly  182 . Furthermore, while wheels  198  are shown as maintaining spray-head assembly  28  a fixed distance from the surface upon which material is to be removed, other mechanizations for maintaining spray-head assembly  28  in a spaced relation from the surface from which material is to be removed can be used. Thus, such variations are not to be regarded as a deviation from the spirit and scope of the present teachings.