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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a ballast tank mountable to an excavator. More particularly, the present invention relates to a tank mountable to excavating equipment for holding fluid for both ballast and fire fighting purposes. 
     2. Description of Related Art 
     Vehicles adapted for delivery of pressurized fluids are well known and widely used in fire fighting, agriculture and construction site applications. Movable vehicles are practical for applications requiring mobility and delivery of large volumes of fluid under pressure. 
     The majority of fire fighting vehicles are highly specialized and designed with large storage fluid tanks and high pressure pumps to deliver fluid to a fire from a relatively safe distance. Examples of such vehicles can be found in U.S. Pat. No. 5,301,756 granted on Apr. 12, 1994 to Robert G. Relyea for a “Vehicle Mounted Aerial Lift”, and U.S. Pat. No. 5,788,158 granted on Aug. 4, 1998 to Robert G. Relyea for an “Automatic Leveling Fluid Nozzle for Aerial Boom”. 
     Other designs known to the inventor for general fluid spraying equipment mountable to a vehicle include U.S. Pat. No. 5,199,196 granted on Apr. 6, 1993 to Paul M. Straley for an “Earth Grading Soil Compaction Tractor with Water Spray Capability”, U.S. Pat. No. 3,016,201 granted on Jan. 9, 1962 to Oren D. Brogden for a “Tunnel Cleaning Machine” and U.S. Pat. No. 3,055,594 granted on Sep. 25, 1962 to Harold K. Nansel for a “Boom-Type Spraying Means”. 
     There exist applications where it is desirable for a fire fighting vehicle to be able to get close to the fire. For example, in some cases, simultaneous delivery of pressurized fluid and penetration and removal of burning debris is desirable. Such work often occurs in forest fires or at building sites where some or all of the structure has collapsed. To work in such conditions requires a vehicle that is able to operate in the extreme heat adjacent a fire and that is stable and able to maneuvering over terrain strewn with debris. 
     Existing excavating equipment equipped with hydraulically operated buckets at the end of manipulating arms function well to remove debris, however, such equipment is not designed to carry large volumes of fluid for fire fighting nor is it designed to operate in the very hot environment in the vicinity of a fire. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a solution to the problems discussed above. Rather than design a new fire fighting vehicle from scratch, I have developed a multi-purpose tank that is retro-fittable to existing excavating equipment to function as a ballasting means and to provide fluid under pressure for fire fighting operations. 
     Accordingly, the present invention provides a tank for an excavator vehicle having a frame and body with a hydraulically operated bucket and an engine, the tank comprising: 
     a main body mountable to the frame adjacent the engine, the main body having a sealed interior volume; 
     at least one ballast region formed within the interior volume to hold fluid for ballast; 
     at least one discharge region formed within the interior volume to hold fluid for discharge from the tank; 
     at least one valve communicating the at least one ballast region with the at least one discharge region to permit one way flow from the ballast region to the discharge region; 
     a pump having an inlet in communication with the discharge region and an outlet; and 
     a conduit extending from the pump outlet for delivering fluid forwardly of the excavator bucket. 
     In a preferred embodiment, the tank of the present invention includes an additional sealed compartment adapted to retain a fire retardant material, the additional compartment including an outlet in communication with the flexible hose for delivering fluid forwardly of the excavator bucket to mix the fire retardant material with the fluid. 
     Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In drawings which illustrate embodiments of the invention, 
     FIG. 1 is a perspective view of an excavator fitted with a tank according to a preferred embodiment of the present invention; 
     FIG. 2 is a perspective view of the tank of FIG. 1 from the rear; 
     FIG. 3 is a simplified perspective view of the tank from the front; 
     FIG. 4 is a rear end elevation of the tank of FIG. 1; 
     FIG. 5 is a plan view of the tank; 
     FIG. 6 is a side elevation view of the tank; and 
     FIG. 7 is a detail view of the one-way valve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An excavator vehicle  12  fitted with the tank  11  of the present invention is illustrated in FIG.  1 . The excavator vehicle  12  has a cab  20  mounted on a frame  25 . An articulated arm  14  is pivotally mounted at point  16  to the frame and extends forwardly therefrom. Arm  14  has an additional pivot point  15  intermediate its length and terminates in an excavating bucket  18 . A pair of caterpillar tracks  22  allow the excavator to move over rough ground. The excavator is rotatably mounted to the frame  25 . An engine  23  is positioned rearwardly of cab  20  to provide power. 
     As best shown in FIGS. 2 and 3, the tank  11  of the present invention comprises a main body mountable to frame  25  adjacent engine  23 . The main body is preferably formed from a series of welded steel plates to define a sealed interior volume. The interior volume is divided into at least one ballast region  30  to hold fluid for ballast and at least one discharge region  32  to hold fluid for discharge from the tank under pressure. While regions  30  and  32  have conveniently been labeled “ballast” and “discharge” regions, respectively, it will be appreciated that both regions inherently act as ballast due to the weight of the tank plates and the weight of the fluid within each region. 
     Tank  11  is advantageously mounted towards the rear of the excavator vehicle  12  and has sufficient fluid capacity to operate as a ballasting device to increase the stability of the excavator vehicle in operations requiring excavation of burning debris with the bucket  18 . Conventionally, excavator vehicles are provided with removable ballast in the form of concrete weights that are attached at the rear of the vehicle. Different weights can be attached depending on ballast necessary to stabilize the vehicle. The tank  11  of the present invention replaces these weights and makes them unnecessary. 
     As best shown in FIG. 3, tank  11  is adapted to fit about engine compartment  23  which is shown by a cross-hatched cube to delimit the general volume of the compartment. Preferably, tank  11  is formed in cross-section as an inverted U with uppermost central web portion  35  that extends between two downwardly extending legs  36 . Legs  36  are positionable on opposite sides of the engine compartment to straddle the compartment such that central portion  35  extends over top the engine. Legs  36  and connecting central web portion  35  are hollow and define the ballast region  30  of the tank. A sealable inlet  37  is provided in central web portion  35  to allow fluid to be introduced into ballast region. 
     An end portion  38  extends across the downwardly extending legs  36  at the rear of the inverted U tank to enclose and cover that end. The end portion  38  has a generally rounded outer side wall  40 . In the illustrated embodiment, the hollow interior of end portion  38  defines the discharge region  32  of the tank. A separate inlet  39  is formed in the top surface of end portion  38 . 
     Legs  36 , central web portion  35  and end portion  38  surround on three sides an open central region  42  positionable over the engine to enclose the engine at the top, sides and at one end in order to cover and protect the engine from the heat and burning ash of a fire. Although the tank is illustrated substantially as a generally U-shaped body to perform its protective function, those skilled in the art will recognize that various other shapes are possible as long as the engine compartment is substantially enclosed. 
     To permit access to the engine compartment  32  for routine maintenance such as oil changes or spark plug changes, there is a central opening  44  through central web portion  35 . As best illustrated in FIG. 3, the central opening  44  is covered by a pair of perforated hinged covers  46 . The covers  46  are hinged to tank  11  by hinges  48  adapted to permit opening of the covers to the position shown in FIG. 3 to provide useful access to the engine compartment  23 . 
     Referring to FIGS. 2 and 4, end portion  38 , which defines discharge region  32 , includes a centrally positioned pump  50 . Pump  50  has an inlet in communication with discharge region  32  and an outlet that directs fluid under pressure via a riser pipe  52  to a conduit  54  that extends from tank  11  to deliver fluid forwardly of excavator bucket  18 . Pump  50  is preferably a hydraulic pump which is driven hydraulic motor  51  external to the discharge tank. It will be apparent to a person skilled in the art that other types of pumps can be used in the discharge region  32 . Preferably, pump  50  is a high capacity pump that is able to discharge fluid at a rate of approximately 15 gallons/minute at 300 psi pressure. 
     To strengthen and brace end portion  38 , plates  55  extend within discharge region  32  on either side of pump  50 . Lower openings  57  in plates  55  permit fluid flow to the pump. Plates  55  also act as partitions to limit the tendency of fluid in the discharge region to move or “slosh” within the tank while the excavator is moving. This is important to prevent shifting of large volumes of fluid in the discharge region  32  which could adversely affect the stability of the excavator. 
     In the arrangement illustrated in FIG. 4, pump  50  can be provided with inlet pipes that extend from the raised surface  59  on which the pump is mounted to the floors  61  of end portion  38  to provide the capability for the pump to scavenge all the fluid in the discharge region  32 . 
     As best shown in FIGS. 1 and 6, conduit  54  for delivering fluid from pump  50  is preferably formed from a series of rigid pipe sections coupled to flexible hose sections to accommodate pivoting movement of articulated arm  14 . For example, as shown in FIG. 6, the section  54   a  extending from the end of riser pipe  52  to coupling  56  is a rigid pipe. Since the L-shaped pipe section  55  protruding from tank end portion  38  may be vulnerable to mechanical damage, a protective shield  63  is preferably mounted adjacent the pipe. At coupling  56 , rigid pipe  54   a  is joined to flexible hose  54   b  which is able to flex to permit movement of arm  14  at pivot point  16 . Hose portion  54   b  is made from a fire retardant material in order to function in the vicinity of a fire. Along the length of arm  14 , there are rigid sections  54   a  to anchor the conduit  54  to the arm so that the conduit moves with the arm and flexible sections  54   b  adjacent pivoting points. Conduit  54  terminates at a nozzle  60  mounted adjacent excavator bucket  18 . Nozzle  18  can be mounted directly to the excavator bucket or to segment  17  of arm  14 . Preferably, nozzle  60  is positioned such that fluid under pressure from the nozzle is directed at objects directly in front of the bucket. 
     FIG. 4 is a rear end view and FIG. 5 is a top view of tank  11 . These views are useful for showing the arrangement of the ballast regions  30  and the discharge region  32  of the tank. Ballast regions  30  occupy the downwardly extending legs  36  and the central web portion  35  of tank  11 . To ensure the structural rigidity of the tank, a series of generally L-shaped gusset plates  62  are welded into the upper corners of legs  36  adjacent the front comers of opening  44  through the central web portion  35 . Plates  62  also act as baffles or partitions that tend to limit movement or “sloshing” of the ballast water in region  30  during normal operation of the excavator. 
     Ballast regions  30  are separated from discharge region  32  by partitions  65  best shown in FIG.  5 . These partitions divide and seal regions  30  and  32  into separate compartments. At least one valve communicates ballast region  30  with discharge region  32  across partition  65  to permit one way flow of fluid from the ballast region to the discharge region. In the illustrated embodiment, two valves  70  are provided to control the flow of fluid as best shown in FIGS. 5,  6  and  7 . The valves are located at opposite sides of the tank at the lower outer edges of discharge region  30 . 
     FIG. 7 is a detail view of the structure of valve  70 . The valve  70  comprises a sealing member  72  that is mounted for vertical movement along post  74  which is rigidly mounted to partition  65 . Sealing member  72  is positioned above a valve chamber  78  that extends between ballast chamber  30  and discharge chamber  32 . Valve chamber  78  includes an inlet  80  that communicates with ballast region  30  and an outlet  76  that communicates with discharge region  32 . Outlet  76  is sealed or opened by vertical movement of sealing member  72  on post  74 . Outlet  76  and sealing member  72  are formed such that flow through outlet  76  is one way from valve chamber  78  to discharge region  32  in the direction shown by arrows  77 . While a specific valve arrangement is shown in the Figures, it will be readily apparent to a person skilled in the art that an alternative one way valve such as a flap valve can be used. 
     A threaded drain plug  82  is provided to permit draining of the valve chamber  78  and ballast region  30 . Similarly, as best shown in FIG. 4, threaded drain plugs  83  are formed in the base of end portion  38  to permit independent draining of discharge region  32 . 
     Fluid in ballast region  30  is free to flow through inlet  80  into valve chamber  78 . Only when the pressure in valve chamber  78  exceeds the pressure in discharge region  32  will valve  70  open to allow water to flow into discharge region  32 . The pressure in discharge region  32  will decrease as pump  50  is operated to discharge fluid through conduit  54 . In this fashion, fluid is supplied to discharge region  32  as needed from ballast region  30 . This approach tends to minimize unnecessary movement or “sloshing” of fluid within a region of the tank or between regions to ensure maximum stability. 
     Referring to FIGS. 5 and 6, the tank of the present invention preferably includes a sprinkler system  90  to spray water under pressure to various regions of the engine compartment  32 . Sprinkler system  90  comprises an additional conduit  92  in communication with pump  50  for delivering fluid as a spray over various areas of the engine. Preferably, conduit  92  extends downwardly and rearwardly from conduit  50  at coupling  93  to extend under central web portion  35  and into engine compartment  32 . Conduit  92  branches into an array of various smaller diameter pipes that terminate in sprinkler heads  94  that are positioned adjacent engine compartment components such as the engine block, the radiator, battery, the oil pump, the fuel pump and the hydraulic lines. A valve  95  controls the flow of fluid through conduit  92  and to sprinkler heads  94 . Valve  95  can be operated manually from the cab or a temperature sensor can be installed in engine compartment  32  to monitor the temperature and open valve  95  if the temperature rises above a pre-determined level. 
     Spraying fluid into engine compartment  32  has been found to lower the temperature in the compartment by 20-30° F. which improves the ability of the engine to operate in the very hot environment adjacent a fire. Also, the water spray produced by sprinkler heads  94  will tend to put out any fires that might be ignited in the engine compartment due to fly ash or other burning debris entering the engine compartment. This makes an excavator equipped with the tank of the present invention safer to operate in and around a fire. 
     Tank  11  is preferably mounted to the excavator via a pivoting joint  96  which is best shown in FIGS. 4 and 6. The main frame of the excavator is typically formed with rearwardly extending, spaced parallel arms  27 . The base of end portion  38  is formed with a channel  97  having inside vertical edges  97   a  formed with recesses  98 . Hinge plates  99  with outwardly extending pins  110  are mounted by a series of fasteners  112  to arms  27  of the main excavator frame. Pins  110  are rotatably received in recesses  98  to define an axis for pivoting of the tank. As best shown in FIG. 6, tank  11  pivots about pins  98  in the direction indicated by arrow  114  such that the front end of the tank is raised to clear engine compartment  32  to provide full access to the engine for major work without having to completely remove the tank. Of course, it is necessary to substantially drain regions  30  and  32  of the tank before attempting to pivot the tank about pins  98 . When tank  11  is in the operating position illustrated, the base of legs  36  preferably rest on the cat walks  140  that extend about the framework of the excavator. In addition, the lower front ends of each leg  36  are formed with anchor plates  142  that can be fixed to the cat walk by fastener  144  to secure the tank in place. 
     To pivot the tank when fasteners  144  are released, an actuator in the form of a hydraulic cylinder  116  (FIG. 6) is preferably provided. Hydraulic cylinder  116  has an end  118  pivotally mounted to excavator frame  25  and an opposite end  120  pivotally attached to the inside face of end portion  38 . As cylinder  116  is extended or shortened, tank  11  will pivot about pins  98 . 
     As best shown in FIGS. 2 and 6, an auxiliary tank  100  can be mounted on the front end of tank  11 . Auxiliary tank  100  is provided to hold a flame retardant, for example foam, that may be mixed with water from the discharge region  32  of the main tank  11  or dispensed alone for short period. Auxiliary tank  100  is connected to conduit  54  via line  102 . A valve  104  in line  102  is controlled remotely from the cab of the excavator to allow the operator to control the amount of foam being delivered to conduit  54 . An inlet  106  for material into the auxiliary tank is provided in the top surface of the tank for convenient filling. 
     A tank according to the illustrated embodiment of the invention manufactured from steel plate will weigh approximately 4,500 pounds empty. Ballast regions  30  can be filled to add approximately 4,000 pounds to the weight. Similarly, if discharge region  32  is filled, the tank will increase in weight by a further 4,000 pounds. By filling the ballast regions  30  and the discharge region  32  with a fluid to different levels, a desired weight distribution in the tank can be initially established. As fluid is discharged, the tank will become lighter. 
     Operation 
     With reference now to FIGS. 1,  2  and  3 , the operation of an excavator equipped with the tank  11  of the present invention will now be described. Tank  11  has been filled to capacity with water and conduit  54  is fully extended with nozzle  60  directed towards the fire by appropriate positioning of articulated arm  14 . 
     To begin pumping of water, the operator switches on pump  50  to move water from discharge region  32  into conduit  54  for discharge through nozzle  60 . The water can be directed at a particular area of a fire by manipulation of arm  14  to assist in fire fighting efforts. In addition, in operation in a forest fire, bucket  18  of the excavator can be used to dig up underground fires and break up burning debris. Prior to material being loaded into bucket  18 , it can be doused with water from nozzle  60  to extinguish burning material or prevent subsequent ignition. The excavator is particularly useful for rapidly forming a fire break by clearing a zone of flammable material adjacent a fire to prevent the fire from spreading. 
     As well as performing as a reservoir for fire fighting water, tank  11  also functions to ballast and stabilize the excavator to which it is mounted. This is particularly important in forest fire fighting environments where the ground over which the excavator is moving may be naturally uneven or may be covered with burnt or burning debris. 
     Tank  11  also serves to cover and protect the engine compartment of the excavator. The engine compartment with oil and gas lines is potentially ignitable by flying ash or other burning debris from a fire. The tank of the present invention provides a physical cover to protect the engine and the sprinkler system disposed in the engine compartment serves to prevent fires from developing and provides some additional cooling of the engine. 
     While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Summary:
A tank for an excavator vehicle having a frame and body with a hydraulically operated bucket and an engine, the tank comprising a main body mountable to the frame adjacent the engine. The main body has a sealed interior volume with at least one ballast region formed within the interior volume to hold fluid for ballast and at least one discharge region formed within the interior volume to hold fluid for discharge from the tank. There is also at least one valve communicating the ballast region with the discharge region to permit one way flow from the ballast region to the discharge region. A pump having an inlet communicates the discharge region with an outlet. A conduit extends from the pump outlet for delivering fluid forwardly of the excavator bucket. The tank provides ballast for stabilizing the excavator and fluid for fire fighting purposes making the tank useful in fire fighting situations where simultaneous delivery of pressurized fluid and penetration and removal of burning debris is desirable. Such work often occurs in forest fires or at building sites where some or all of the building structure has collapsed. To work in such conditions requires a vehicle that is able to operate safely in close proximity to heat and flames and that is stable and able to maneuvering over terrain strewn with debris.