Abstract:
An apparatus for distributing fluid onto a hydrometallurgy leach field consists of individual modules having structure for operatively coupling the modules to one another to form the apparatus. Each module, which alone can form a fluid distribution apparatus, includes a frame and an elongated reel assembly on which a plurality of individual distributors, such as perforated hoses, are carried at axially spaced positions along the elongated reel assembly. A fluid supply conduit carries fluid from a fixed fluid supply line through the elongate reel assembly to each of the hoses carried on the elongated reel assembly and to an adjacent module. The frame is supported at its ends by frame translating mechanisms, preferably endless track crawler units, which serve to selectively move the apparatus forward and rearward. Adjacent modules are coupled at respective ends thereof to a common frame translating mechanism, thus coupling the adjacent modules to one another. To distribute fluid onto the leach field, the apparatus is moved forward over the leach field heap while simultaneously unrolling the plurality hoses to deploy the hoses in a closely spaced parallel arrangement over the leach field heap. With the hoses deployed, fluid is run through the hoses and out of the perforations thereof and onto the leach field surface. After leaching is complete, the hoses are then rolled onto the elongated reel assembly and the apparatus is moved to a different part of the leach field to re-deploy the hoses.

Description:
This is a division of application No. 09/063,385, filed Apr. 21, 1998, now U.S. Pat. No. 6,009,956. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for distributing fluid to a leach field in the practice of the art of hydrometallurgy. 
     The art of hydrometallurgy is described in some detail in U.S. Pat. No. 5,005,806, the disclosure of which is hereby incorporated herein by reference. In essence, hydrometallurgy is the art of recovering metals from ores by separating a solution of the metal in the form of a salt from the ore, then decomposing the metallic salt in such a way to cause precipitation of the metal from the solution. The leaching solution, or lixiviant, used depends on the particular metal being leached from the ore. For example, gold and silver are typically reclaimed from low grade ore using lixiviants generally constituting aqueous solutions of sodium cyanide mixed with oxygen to convert the metal to a soluble salt from which the metal can be recovered by precipitation. Leaching solutions of sulfuric acid or sulfuric acid-sulfate are typically used for leaching copper from an ore. 
     In the commercial practice of hydrometallurgy, a bed of run-of-mine or granular low grade ore, known as a heap, is spread over an impervious base or pad which may comprise sheets of plastic film, asphalt and/or compacted clay. Crushed ore is normally heaped onto the pad to a depth to 10 to 30 feet and leveled off at the top of the heap. The ore is typically pre-crushed to a desired size. For example, for copper mining, the ore may be crushed to one quarter inch granular size. 
     After the heap has been prepared, the target metal is leached from the ore by circulating the leaching solution through the heap in a process commonly known as percolation. To effect percolation, the solution is distributed over the top of the heap and permitted to seep down through the heap to the impervious pad. The impervious pad is typically sloped toward a drain pipe or channel for recovering the metal laden solution. The liquid that is distributed over the top of the heap may be a leaching solution comprising water mixed with a leaching agent, or a leaching agent may be premixed with the ore before the ore is spread onto the heap and relatively pure water is percolated through the heap. For example, in copper ore mining, sulfuric acid is mixed with one quarter inch crushed copper ore before the ore is spread onto the heap, and pure water is percolated through the heap to mix with the sulfuric acid and leach the copper from the ore. 
     Various systems have been used for distributing water over a leach field. For example, sprayers or sprinklers may be positioned at various locations on the heap to spray and distribute water or leaching solution over the top of the surface. Liquids distributed in such a manner are prone to rapid evaporation and degradation by exposure to air and ultra violet rays, and in addition, can be prone to freezing in cold weather operations. In addition, spraying techniques can result in surface puddling and run-off, raising the threat of channeling problems and potentials for blowouts. 
     U.S. Pat. 5,005,806 discloses a liquid distribution system which includes main line pipes extending longitudinally along a side of the heap and header pipes extending at spaced intervals from the main line pipe transversely across the heap generally parallel to one another. Extending in both directions across the heap from the header pipes are a plurality of generally parallel, closely spaced tubes. Liquid flows from the main line pipes, into the header pipes and into the tubes, and each tube has a plurality of spaced emitters secured thereon for directing the leaching solution onto the ore bed. 
     The general layout of a conventional copper ore leaching operation is shown in FIG.  1 . The lay-out of the leach field  10  is generally that of an oval track having a first straight portion  12  a second straight portion  14  and first and second turning areas  20 ,  22 . To make such an operation commercially viable, it is typically necessary that such a field be extremely large. For example, in commercial operations, each of the straight portion  12  and  14  may be up to 400 meters wide and 1.6 kilometers long, and the depth of the heap may be six meters. 
     In the leach field operation shown in FIG. 1, heaps are formed along the first and second straight portions  12  and  14  by a traveling stacker conveyor system  32 , and spent ore is removed from the straight portions by traveling cleaner conveyer system  24 . Copper laden ore mixed with sulfuric acid is brought into the field from a remote crusher and mixer along an underground inlet conveyer  16 . The stacker conveyer assembly  32  branches off the inlet conveyer  16 . Stacker conveyer system  32  includes a stacker conveyer  34  extending transversely across the straight portion  12  or  14  from the inlet conveyer  16 . The stacker conveyer system  32  travels clockwise on the leach field shown in FIG. 1 supported on a plurality of endless track crawlers  36  which are typically power by electrically powered hydraulic systems. A stacker mechanism (not shown) travels back and forth along the stacker conveyer  34  and distributes ore from the conveyer  34  onto the heap. The rate of movement of the stacker conveyer system  32  about the leach field  10  and the rate of movement of the stacker along the stacker conveyer  34  are preferably set so as to create a relatively evenly distributed heap of about  6  meters in depth. The heap is formed only on the straight portions  12  and  14  from the beginning  11  of straight portion  12  to the end  13  thereof and from the beginning  17  of straight portion  14  to the end  15  thereof. 
     In a conventional hydrometallurgy operation, such as that previously described, water is distributed to the heap to effect the leaching percolation in a manner similar to that disclosed in U.S. Pat. No. 5,005,806. That is, main pipes  40  and  38  bring fluid from a remote source to the leach field  10 , a plurality of header pipes (not shown) extend transversely from the pipes  38  and  40  across the leach fields, and pluralities of closely spaced, generally parallel hoses (not shown) extend from the header pipes in both directions across the top of the heap. Rather than using specially designed emitters, however, the hoses are typically perforated at numerous locations along their respective lengths so as to allow fluid to leak therefrom onto the heap. The copper laden solution is directed by the impervious pad beneath the heap toward recovery pipes  42  and  44  which direct the solution to a facility at which the copper can be precipitated from the solution. 
     After the ore has been sufficiently leached, the spent ore is removed from the field by a traveling cleaner conveyer system  24 . Cleaner conveyer system  24  comprises a conveyer  30  supported for clockwise translation about the leach field  10  on a plurality of endless track crawler mechanisms  28 . A cleaner mechanism  26 , typically comprising a rotary shovel device, travels up and down the cleaner conveyer  24 , scooping spent ore from the heap onto the conveyer  30 , which directs the spent ore towards the central underground conveyer and away from the leach field  10  through an outlet conveyer  18 . Accordingly, as shown in FIG. 1, the area to the right of the cleaner conveyer system  24  is a cleaned area from which spent ore has been removed, and the area to the left of the conveyer system is a heap of spent ore or ore which is presently undergoing a percolation procedure. 
     It can be appreciated that the stacker conveyer system  32  and the cleaner conveyer system  24  follow each other about the leach field  10 , the stacker conveyer system  32  distributing a heap of ore, and the cleaner conveyer system  24  removing the spent ore after percolation has been performed on the ore. The turning areas  20  and  22  are provided so as to permit the continuous forward translation of the stacker conveyer system  32  and cleaner conveyer system  24 . 
     The previously described method of distributing water over the leach fields suffers from a number of disadvantages. The header pipes extending across the heaps from the main pipes  38  and  40  and the numerous perforated tubes extending from the header pipe across the heaps are typically assembled and disassembled using manual labor. The shear magnitude of the manual effort necessary to assemble and disassemble the fluid distribution systems can be appreciated when considering the overall size of the leach fields, typically 400 by 1600 meters in size. Accordingly, the assembly and disassembly of the fluid distribution system is incredibly labor and time intensive. In addition, the numerous tubes and pipes which must be manually assembled and disassembled are subject to damage and entanglement due to their frequent handling. Because the pipes and tubes are to be manually handled, they must necessarily be of light weight materials which makes them more susceptible to damage, especially in the rugged environment of a leach field operation. Also, because of the frequent connecting and disconnecting of the header pipes and the frequent connecting and disconnecting of the tubes to and from the header pipes, it is necessary that the connectors used be connectors capable of easy connecting and disconnecting. Such connectors are typically susceptible to wear and fatigue and therefore are prone to malfunction and require frequent replacement. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a robust mechanized apparatus for deploying and retrieving a fluid distributing hose arrangement that overcomes the disadvantages suffered by prior art leach field fluid distribution systems which require manual deployment and retrieval. 
     This object is achieved by providing a mobile apparatus for distributing fluid to a surface. The apparatus comprises a frame structure, an axially elongated reel assembly rotatably carried by the frame structure, a plurality of flexible tubes carried on the axially elongated reel assembly at different axially spaced positions along the axially elongated reel assembly, and a frame transport mechanism constructed and arranged to support the frame structure and to transport the frame structure in a forward or rearward direction. The axially elongated reel assembly further includes an interior fluid flow passage to transmit fluid from an external fluid supply to each of the plurality of flexible tubes. 
     The mechanized apparatus drastically reduces the amount of manual labor required for deploying and retrieving the hose system. In addition to the savings of manual labor costs, the apparatus provides further cost effectiveness in that, because the pipe and hose arrangement does not require manual deployment, heavier, more robust components may be used, which are more durable than the components used in prior art arrangements. Accordingly, less frequent part replacement and less down time due to breakdowns would be expected. 
     It is a further object of the present invention to provide an apparatus that is modular so that a fluid distribution apparatus of a size needed for a commercial hydrometalurgy leach field can be easily assembled and disassembled and further to provide an apparatus that can be accommodated by existing leach field set-ups with little or no modification of the leach field required. 
     This object is achieved by a mobile apparatus for distributing fluid onto a surface. The apparatus comprises a plurality of elongated frames arranged end-to-end, each of the elongated frames having structure for operatively coupling opposed ends thereof to adjacent elongated frames. A frame propulsion mechanism is associated with each end of each elongated frame for supporting each end and for propelling the plurality of elongated frames in unison. Each elongated frame includes propulsion mechanism coupling structure at each end thereof, and each said frame propulsion mechanism includes frame coupling structure constructed and arranged to (1) be engaged by the propulsion mechanism coupling structure of a first associated elongated frame to operatively couple the first associated elongated frame to the frame propulsion mechanism and (2) to be engaged by the propulsion mechanism coupling structure of a second associated elongated frame adjacent to the first associated elongated frame to operatively couple the second associated elongated frame to the frame propulsion mechanism and to couple the second associated elongated frame to the first associated elongated frame. An axially elongated reel assembly is rotatably carried by each elongated frame, each axially elongated reel assembly being constructed and arranged to support thereon a plurality of lengths of flexible tubing wound upon the axially elongated reel assembly at different axial positions therealong. Each axially elongated reel assembly includes a fluid passageway extending along the axially elongated reel assembly, primary connection devices disposed at opposite ends of the fluid passageway for coupling an end of the fluid passageway in fluid communication with either an external fluid source or a fluid passageway of an axially elongated reel assembly of an adjacent elongated frame, and a plurality of secondary connection devices disposed at spaced apart positions along the fluid passageway for connecting a length of flexible tubing in fluid communication to the fluid passageway. 
     These and other features of the present invention as well as methods of use and construction will become more apparent during the course of the following detailed description and appended claims. The invention may best be understood with the reference to the accompanying drawings wherein an illustrative embodiment is shown. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic plan view of a leach field operation on which the apparatus for distributing fluid to a leach field of the present invention is employed; 
     FIG. 2 is a broken rear elevation of the apparatus of the present invention; 
     FIG. 3 is a perspective view of a frame and reel assembly of the apparatus of the present invention; 
     FIG. 4 is a partial plan view of the apparatus of the present invention; 
     FIG. 5 is a rear elevation of the frame and reel assembly of the apparatus of the present invention; 
     FIG. 6 is a cross section along the line “VI—VI” in FIG. 5; 
     FIG. 7 is an end view showing the frame and reel assembly as well as an endless track crawler unit of the apparatus of the present invention; 
     FIG. 8 is an end view similar to the end view of FIG. 7 showing the ability of the crawler unit to articulate to accommodate transitions in slope; 
     FIG. 9 is an end view of an alternate embodiment of a propulsion and reel-rotating mechanism of the apparatus of the present invention; 
     FIG. 10 is a broken perspective view of a chisel plow assembly of the apparatus; and 
     FIG. 11 is an enlarged perspective view of a frame support bracket of the apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For convenience in the following description, various directional or other spatial references are made with regard to references to the drawings. It is understood, however, that such references, including without limitation, upper, lower, top, bottom, left, right, lateral, or longitudinal, are made for convenience only and should not be construed to be limiting on the invention described herein. 
     An apparatus for distributing fluid to the leach field  10  of FIG. 1 is designated generally by reference number  50 . In the illustrated leach field  10 , four apparatuses  50  are shown. The two apparatuses  50  shown on the upper straight portion  12  are coupled to fluid pipe  40  and the two apparatuses  50  shown on the lower straight portion  14  are coupled to the main pipe  38 . 
     Each apparatus  50  preferably includes a plurality of individual modules  100  coupled together end to end to form the apparatus  50 . As shown in FIG. 2, each individual module  100  includes a frame  110  supporting therein an axially elongated reel assembly  170 . Each frame  110  is supported at opposite ends thereof by a frame translating mechanism, preferably in the form of an endless track crawler unit  250 , and adjacent frame assemblies  110  of adjacent individual modules  100  are coupled to one another at the crawler unit  250  positioned therebetween. Each of the crawler units  250  is power driven either in a forward or rearward direction so that the entire apparatus  50  can translate back and forth on the leach field  10  and can travel in a clockwise direction about the leach field track as do the stacker conveyer system  32  and the cleaner conveyer system  24  described above. 
     Each frame  110  is preferably about forty meters long. That is, the spacing between adjacent crawler units  250  is forty meters. The spacing between the crawler units  250  of the fluid distributing apparatus  50  is preferably the same as the spacing between the crawler units  36  of the stacker conveyer system  32  and the spacing between the crawler units  28  of the cleaner conveyer system  24 . The spacings between the adjacent crawler units of the fluid distributing apparatus  50 , the stacker conveyer system  32  and the cleaner conveyer system  24  are preferably all the same because as each system traverses the leach field  10  and passes over the underground inlet conveyer  16  at the first turning area  20  and outlet conveyer  18  at the second turning area  22 , the respective crawler units travel over spaced-apart bridge structures (not shown) which support the weight thereof as the system passes over conveyers. The bridge structures are spaced apart by the same distance as the crawlers. Because the spacing between crawler units  250  of the fluid distributing apparatus  50  is the same as the spacings between the crawler units of the cleaner and stacker conveyor assemblies, and, therefore, the same as the spacing between the bridge structures, the fluid distributing apparatus  50  can be used in a conventional leach field arrangement without requiring substantial modification of the leach field. 
     As shown in FIGS. 2-5, the frame  110  preferably comprises front and back upper longitudinal stringers  114  arranged in a spaced apart parallel relation and lower front and back longitudinal stringers  112  disposed directly below the upper longitudinal stringers  114 . The upper and lower longitudinal stringers  114 ,  112  are connected to one another and spaced apart from one another by a plurality of vertical stringers  116  extending therebetween. The front and back longitudinal stringers are spaced apart from and coupled to one another by upper lateral stringers  120  and lower lateral stringers  124  extending therebetween. Lateral angled brace members  122  extend diagonally between the front and back upper longitudinal stringers  114  and vertical angled brace members  118  extend from the upper longitudinal stringers  114  to lower longitudinal stringers  112  between adjacent vertical stringers  116 , such as shown in FIG. 2, or as shown in FIG.  3 . The angled brace members  122 ,  118  provide additional vertical, lateral, and torsional stiffness to the frame  110 . 
     The various frame members are preferably constructed of tubular and/or angular steel material and are held together by mechanical fasteners, such as bolts or rivets, and/or by welding. 
     As shown in FIGS. 3,  5  and  6 , the axially elongated reel assembly  170  is supported within the frame  110 . The reel assembly  170  includes a reel  172 , which is preferably an elongated continuous tubular structure, and a plurality of axially spaced, radially extending divider members  174  disposed along the reel  172 . 
     The reel  172  is mounted for rotation about its longitudinal axis of rotation within the frame  110  by reel support assemblies  180 ,  190 . Reel support assembly  180  includes upper roller elements  182  rotatably mounted on an upper cross brace  184  and lower roller elements  188  rotatably mounted on a lower cross brace  186 . 
     The upper and lower roller elements  182 ,  188  are arranged so that a diagonal line connecting diagonally opposed upper and lower roller elements passes through the axis of rotation of the reel  172 . As shown in FIG. 6, the lower roller elements  188  are arranged so as be symmetrically spaced from the center of the reel  172  and are positioned so that an angle θ between a vertical line extending through the axis of rotation of the reel  172  and a line extending through the axes of rotation of the reel  172  and a roller element  188  is preferably in the range 30 to 40°, and most preferably about 35°. With the roller elements  188  disposed in this manner, the reel  172  is supported in a stable manner on the roller elements  188  with a large component of the weight of the reel  170  acting through the connection point of the roller element  188  to the lower cross-brace  186 . 
     The second reel support assembly  190  is essentially identical to the first reel support assembly  180 . Assembly  190  includes upper roller elements  192  supported on an upper cross member  194  and lower roller elements  198  supported on a lower cross member  196 . 
     The reel support assemblies  180  and  190  are preferably space inwardly from the outer ends of the reel  172  so as to minimize bending moments acting on the reel  172  due to the weight thereof. 
     It can be appreciated that the reel  172  is able to rotate within the reel support assemblies  180  and  190 . The reel assembly  170  is preferably constructed and arranged for powered rotation. Such powered rotation could be provided by providing powered rotation in one or more of the roller elements  182 ,  188 ,  192 ,  198 , or the reel  172  may be coupled to a rotating shaft of a power unit (not shown) by a power transmission mechanism such as a gear arrangement or a chain and sprocket arrangement. 
     In addition, the reel assembly  170  is preferably coupled by a rotation transmission mechanism (not shown) to the translation of the module  100  so as to selectively rotate in a hose unrolling direction as the module  100  moves forward and to selectively rotate in a hose rolling direction as the module  100  moves backward. 
     The reel assembly  172  preferably also includes a brake mechanism for selectively preventing rotation of the reel  172 . Such a brake mechanism could be provided in one or more of the roller elements  182 ,  188 ,  192 ,  198 , which would also brake the reel  172  because of the frictional contact between the rollers and the reel. Alternatively, a brake mechanism could be provided which directly engages the reel  172 . 
     Each fluid distribution apparatus  50  is coupled to one of the main pipes  40  and  38 , such as by a flexible hose  104  connected to respective couplings at the pipe  40  or  38  and the distribution apparatus  50 . As shown in FIGS. 2,  4  and  6 , each axially elongated reel assembly  170  of each module  100  has a conduit  175 , preferably a pipe, extending centrally therethrough and defining an interior fluid passage. The individual modules  100 , are coupled to one another to permit fluid to flow one to the next by couplings  178  connecting the pipes  175  of adjacent units. To accommodate relative movement of one of the modules  100  with respect to an adjacent module  100 , coupling  178  is preferably a spool type expansion joint used for connecting adjacent sections of piping. A valve  177  is preferably provided for shutting off fluid flow through pipe  175 . 
     A plurality of individual fluid distributors, preferably in the form of fluid distributing, elongated flexible tubes  176  are individually coupled to the central pipe  175  of each module  100 . The flexible tubes  176  may distribute fluid therefrom in any of a variety of ways. The tubes  176  may be porous or perforated, with holes arranged in any manner, such as linearly, randomly, or in regular patterns, or the tubes may include spaced-apart discrete distributing elements, such as water emitting fittings or sprinklers. In the preferred embodiment, the fluid distributors comprise lengths of flexible tube  176  coupled at one end to central pipe  175  and closed at a remote end and having a series of perforations formed along the length. For simplicity, the fluid distributors will be referred to hereinafter as “hoses” or “perforated hoses”. The hoses  176  are deployed behind the apparatus  50  in a side by side, generally parallel arrangement, and fluid flows through each of the hoses  176  and through the perforations thereof so as to be distributed over the leach field for percolating through the ore. The hoses  176  may be rolled up onto the reel assembly  170  to transport the hoses from one location on the leach field to another. 
     A flow rate sensitive shut-off valve is preferably provided between the main pipes  38 ,  40  and the apparatus  50  to shut off flow to the apparatus if flow rate into the apparatus exceeds a predefined threshold level. Accordingly, if a pipe or hose break should occur in the apparatus, resulting in high fluid flow rate, fluid to the apparatus is shut off. The shut-off valve may be used in conjunction with a visible and/or audible alarm to notify operators that a shut off has occurred. 
     Each hose  176  is preferably coupled to the reel  172  and the fluid supply by means of a pipe  177  extending radially from the central pipe  175  through an outer wall of the reel  170  and having an L-shaped end fitting  173  connected to the hose  176 . Alternatively, each hose  176  could be connected to a flexible fitting at the end of a conduit emanating from the central pipe  175  and extending through the reel  172 , the flexible fitting permitting the hose  176  to be directed in a circumferential direction with respect to the reel  172 . 
     Each hose  176  is preferably perforated black polyethylene tubing having a preferred outside diameter of ⅝ inches. To withstand the large tensile stresses to which the hose  176  may be subjected when dragging the hose across the heap during forward translation of the fluid distribution apparatus  50  or during wind-up of the hose  176  while the fluid distribution apparatus  50  is kept stationary, it may be desirable to provide a length of hose extending from the fitting  173  for a specified distance which is of greater strength than the remaining portion of ⅝ inch black polyethylene hose. Such an initial hose portion may comprise hydraulic power grade reinforced hoses. 
     Each module  100  preferably includes a tube guide  200  for directing the hoses  176  extending off the reel  172  to a position below the lower longitudinal stringer  112  of the frame  110 . The tube guide  200  includes mounting brackets  202 ,  206  extending down from lateral cross members  132  and  155 , respectively, and a longitudinal guide bar  204  extending therebetween. Guide bar  204  may be a cylindrical member rotatably mounted in the brackets  202  and  206  so as to facilitate movement of the hoses  176  with respect to the guide  200 . Also, guide bar  204  preferably has a diameter large enough so as to avoid placing a sharp bend or kink in the hoses  176 , bent therearound. 
     Each module  100  preferably also includes a frame mounted sprayer system  205  as shown in FIG.  5 . Sprayer system  205  includes a pipe or other suitable conduit  210  extending longitudinally along one of the lower longitudinal stringers  112  and is coupled to the fluid pipe  175 . A plurality of equally spaced sprayer units  208  are provided along the longitudinal extent of the pipe  210  and can be used to selectively spray fluid onto the heap directly from the frame  110  with the apparatus  50  translating forward or backward or with the apparatus  50  stationary. 
     The details of the crawler units  250  are shown in FIGS. 7 and 8. The crawler unit  250  includes a frame  251  which comprises middle structure  252  and end structures  254 ,  256 . End wheels  258  and  260  are rotatably mounted within the end structure  254  and  256 , respectively, and an endless track  268  extends about the frame  251  and the end wheels  258  and  260 . Middle structure  252  and end structures  254  and  256  may include a plurality of rotatably mounted roller elements  264 ,  262 ,  266 , respectively, for supporting the endless track  268  in rolling contact therewith. 
     The crawler unit  250  is preferably articulated so that, as shown in FIG. 8, a portion of the crawler can articulate with respect to the remainder of the crawler to accommodate changes in ground slope. Without the ability to articulate, the crawler  250  would merely translate forwardly onto a downwardly sloped grade without contacting any portion of the downwardly sloped grade until the center of gravity of the apparatus was far enough forward and the whole apparatus would tip downwardly in a jolting manner. An articulating crawler unit  250  allows the apparatus to transition onto a downward slope with less jolting to the apparatus. 
     Articulation is provided by a pivot mount  270  between end structure  254  and middle structure  252 , with a gap  290  between the adjacent structures, and a pivot mount  272  between end structure  256  and middle structure  252  with a gap  292  between the adjacent structures. In the illustrated embodiment, the gaps  290 ,  292  between the end structure  254  and middle structure  252  and between end structure  256  and middle structure  252 , respectively, are only provided below the respective pivot points  270 ,  272 . Hard contacts between the end structure  254  and the middle structure  252  and between the end structure  256  and the middle structure  252  are provided above the pivot points  270 ,  272 , respectively, when the crawler  250  is on a level grade so that the ends  254  and  256  are not permitted to articulate upwardly with respect to the middle portion  252 . Upward articulation may be provided, but for the present application, downward articulation is most important so as to minimize sudden tipping of the apparatus when transitioning onto a downward slopping grade. Sudden jolting is usually not a problem when the apparatus transitions onto an upwardly sloping grade, and, therefore, upward articulation of the end structures  254  and  256  is not as important as downward articulation. 
     Each crawler unit  250  would include a track driving mechanism (not shown) including a power plant and a transmission which drives one or both of the end wheels  258 ,  260  to drive the track  268 . In the preferred embodiment, the power plant for the track driving mechanism is an electrically powered hydraulic motor such as is used in the crawler units  36  and  28  of the stacker conveyer system  32  and the cleaner conveyer system  24 , respectively. 
     The reel assembly  170  is preferably coupled to the crawler units by an appropriate transmission mechanism to cause the reel  172  to rotate as the crawler units  250  move apparatus  50  forward or backward. As the distributing apparatus  50  moves forward, the reel rotating transmission can be engaged to cause the reel  172  to unwind each of the hoses  176  as the apparatus moves forward, the amount of hose being unrolled corresponding to the forward distance traveled. With the hoses deployed behind the apparatus  100 , the apparatus can be kept stationary while the hoses distribute fluid over the heap, or the apparatus  50  can move forward to drag the hoses across the heap. To rewind the hoses, the apparatus  50  can be moved in a reverse direction and the reel rotating transmission engaged to rotate reel  172  to wind up the hoses  176  as the apparatus moves backwards. Alternatively, after the hoses  176  are completely unwound from the reel  172 , movement of the apparatus can continue in a forward direction to rewind the hoses on the reel in an opposite direction. 
     Alternatively, a reel rotating mechanism can be provided which works independently of the movement of the crawler units, and the reel can be rotated in the wind up direction while the apparatus is held stationary to drag the hoses towards the apparatus  50  while winding them onto the reel assembly  170 . 
     An example of a reel-coupling transmission is shown in FIG.  9 . The frame  110  is supported and transported by non-articulating crawler unit  350 . Crawler unit  350  includes a main frame  351 , rotatably mounted main wheels  358 ,  368 , guide wheels  364 , and endless track  368 . A coupling wheel  370  is rotatably mounted to frame  110  and is disposed between the crawler unit  250  and the reel assembly  170 . Specifically, coupling wheel  370  is in rolling frictional contact with reel  172  and the track  268 . In the illustrated embodiment, coupling wheel  370  presses track  268  between its outer periphery and the outer periphery of main wheel  368 . When the apparatus moves forward in direction indicated by arrow “A”, the track  268  and main wheel  360  rotate counterclockwise in direction “B”, thus driving coupling wheel  370  clockwise in direction “C”, and ultimately rotating reel  172  counterclockwise in direction “D”. The hoses  176  will unwind from reel  172  as the unit moves forward so as to be deployed behind the unit. The diameters of the main wheel  360 , coupling wheel  370 , and reel  170  are tailored so that the length of hose unwound from the reel corresponds to the distance the unit moves forward. When the apparatus moves backward, opposite to direction “A”, rotations of the main wheel  360 , the coupling wheel  370 , and the reel  172  are reversed, and the hoses  176  are wound up onto the reel  172 . 
     The reel coupling transmission is preferably disengagable by a clutch or other disengaging mechanism so that the apparatus  50  can be moved forward or backward without any corresponding reel rotation. The reel coupling transmission of FIG. 9 preferably includes means, such as a lever mechanism or a hydraulically actuated device, for moving coupling wheel  370  out of engagement with the reel  172  and/or the track  268  to disengage the reel  172  from movement of the crawler unit  350 . 
     When the entire length of the hoses, or some desired, shorter length, is unrolled from the reel, as determined by a spotter or by monitoring the number of reel rotations, the reel can be disengaged to stop hose deployment. The apparatus can then remain stationary while fluid is run through the hoses and onto the heap surface, and/or a brake can be applied to the reel  172  and the apparatus can be moved forward to drag the hoses across the heap surface. 
     In addition, the reel coupling transmission may have additional gearing for reversing rotation of the reel  172  without reversing the direction of translation of the apparatus. For example, in the reel coupling transmission of FIG. 9, if reel coupling wheel  370  were replaced with two coupling wheels, one engaged with the track  368 , one engaged with the reel  172 , and both engaged with each other, rotation of the reel would be reversed as compared to rotation caused by the single coupling wheel  370 . 
     To assemble the apparatus  50  across the width of the heap of the leach field, it is necessary to couple the frames  110  of adjacent modular units  110  with the crawler units  250  and with each other. Each crawler unit  250  includes a number of frame receiving support brackets attached to both sides of the middle structure  252 . In the illustrated embodiment, crawler  250  includes four frame receiving support brackets,  274 , 276 ,  278  and  280  on each side of middle structure  252 . As shown in FIG. 10, each frame receiving support bracket preferably includes a generally horizontal shelf  282  supported therebelow by gusset structures  286  and  288 . The gusset structures  286  and  288  and the shelf  282  are preferably formed of plate steel and are welded to one another and the entire bracket is welded to the outer wall of the middle structure  252 . 
     Each frame  110  includes an inboard coupling structure for engaging one or more of the brackets  274 ,  276 ,  278  and  280  on the side of the crawler unit  250  facing the frame  110  and an outboard coupling structure for engaging one or more of the brackets on an opposite side of the crawler unit  250 . As shown in FIGS. 3 and 5, in the illustrated embodiment, the inboard coupling structure includes longitudinal extensions  142  and  144  extending from the lower longitudinal stringers  112  on one end of the frame  110  and extension  160  and  162  (see FIG.  5 ), on the opposite end of the frame  110 . The extensions  144 ,  142  engage the outer most brackets  274 ,  280  of the crawler unit  250  by resting thereon to support the end of the frame  110  on the crawler unit  250 . 
     The underside of the extension  144 ,  142  may include a hollow, recessed portion for receiving therein a convex surface  284  of the bracket  274 ,  280  as shown in FIG.  10 . The convex surface  284  extended within the recessed portions beneath the inboard extensions  142 ,  144  creates a ball and socket connection which prevents lateral translation of the frame  110  with respect to the brackets  274 ,  280 . 
     In the illustrated embodiment, the outboard coupling structures comprise endwise frame extension  130  and endwise frame extension  150 . Frame extension  130  includes a first angled member  136  extending downwardly from an endmost upper lateral stringer  120  at an angle of preferably around 45°. A vertical member  134  extends down from a lower end of the angled member  136 . A vertical member  140  extends between the end-most upper lateral stringer  120  and the cross member  132 , and a horizontal brace  138  extends between the vertical member  140  and the angled portion  136 . An additional angled member  146  may be provided between the angled portion  136  and the intersection of horizontal brace  138  and vertical member  140 . 
     Similarly, endwise extension  150  includes a first angled member  152 , a vertical member  154  extending downwardly from the free end of first angled member  152 , a vertical member  158  extending between end-most upper lateral stringer  120  and cross member  155 , and a horizontal brace  156  extending between the first angled member  150  and the vertical member  158 . A second angled member  157  between the first angled member  152  and the intersection of the horizontal brace  156  and the vertical member  158  may be provided. 
     The endwise extensions  130  and  150  are constructed and arranged so that the space between the inboard coupling structure and the outboard coupling structure, e.g. between the extension  142  and the first vertical member  134 , is sufficient to accommodate the width of a crawler unit  250  so that when extension  142  and  144  are engaged with the brackets  274  and  280  on a side of the crawler unit  250  facing the frame  110 , the bottom portion of the vertical member  134  engages one of the intermediate brackets  276 ,  278  on the opposite side of the crawler unit  250 . Again, the bottom end of the vertical portion  134  may include a recess to receive the convex surface  284  of the bracket. 
     As shown in FIG. 4, the endwise extensions  130  and  150  on opposite ends of the frame  110  are offset laterally with respect to one another. Thus, two adjacent frames  110  are coupled to an intermediate crawler unit, and therefore to each other, by engaging the longitudinal extensions  142 ,  144  of the first frame and the endwise frame extension  150  of the second frame with three of the four framereceiving support brackets on the side of the crawler unit  250  facing the first frame and engaging the longitudinal extensions  160  and  162  of the second frame and the endwise frame extension  130  of the first frame with three of the four frame-receiving support brackets on the side of the crawler unit  250  facing the second frame. Accordingly, it can be appreciated that the modules  100  can be easily coupled to one another and can also be easily uncoupled from one another if one of the modules  100  in the apparatus  50  must be repaired or replaced. 
     A chisel plow  300 , as shown in FIGS. 2 and 9, may be pulled behind each of the crawler units  250  to loosen up ore compacted by the weight of the distributing apparatus  50 . The chisel plow  300  may comprise a U-shape structure having two arms  302  and  304  extending rearwardly from the crawler unit  250  and pivotally attached thereto at end portions  306  and  308 , respectively. Arms  302  and  304  are connected at the ends thereof by a cross portion  312 . A plurality of chisel teeth  314  extend downwardly from the cross portion  312 , and each tooth  314  has a chisel point  316  for digging into the compacted ore. 
     Because neither the hoses  376  carried by the reel assembly  170  nor the framed mounted sprayer system  204  distribute fluid onto the area of the heap over which the crawlers  250  move, a plow mounted sprayer system  324  is preferably provided. Plow mounted sprayer system  324  includes a first pipe portion  318  extending along one or both the arms  304 ,  302  from the fluid supply on the frame  110 , such as the pipe  175 . A second portion of the pipe  320  extends laterally from the first portion  318  and includes a plurality of nozzles  322  for spraying fluid onto the area of the heap over which the chisel plow has just passed and loosened the compacted ore. 
     It will be realized that the foregoing preferred specific embodiment of the present invention has been shown and described for the purposes of illustrating the functional and structural principles of this invention and are subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.