Abstract:
A method of draining fluid from a self-supporting transportable storage tank having a rear wheel chassis, a rear drain fitting, and a jack assembly at the forward end of the storage tank is disclosed. The forward end of the storage tank is elevated by extending the jack assembly to lift the forward end thereof off the ground. The rear drain fitting is opened to allow fluid to drain from the storage tank. Alternatively, a front drain fitting may be provided, and the storage tank is drained by lowering the rear wheel chassis to lift the rear-end of the storage tank off of the ground, and opening the forward drain fitting.

Description:
This application is a divisional of application Ser. No. 08/819,041, filed on Mar. 17, 1997, U.S. Pat. No. 5,957,500, which was a divisional of application Ser. No. 08/450,111, filed on May 25, 1995, U.S. Pat. No. 5,653,469, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     tanks are currently provided for storing and dispensing fluids, such as fracturing liquids, drilling muds, and the like, for use at an oil or gas well site. Such tanks are also used to receive and hold fluids and chemicals at industrial plants. They are also used on environmental clean-up jobs, as well as spills, to hold fluids until they can be properly disposed of. When empty, these tanks are towed by truck from one site to another, where they are refilled and reused. The tanks usually have lengths of 30 to 40 feet, a height of from approximately 9 to 12 feet, and a width of 8 feet. Various federal, state and local highway ordinances limit the size of these trailers for over-the-road transport. These tanks are constructed to have a large capacity, holding thousands of gallons of liquid; therefore, there is a need to provide a mobile storage tank constructed and arranged to not only increase the storage capacity of the tank for holding fluids at the job site, but also dimensioned to conform to the highway ordinances for over-the-road transport. 
     SUMMARY OF THE INVENTION 
     The mobile storage tank of the present invention is provided with a ladder and manholes which are recessed into the walls of the tank so that a maximum height of twelve feet, six inches, and a width of eight feet, six inches can be obtained, and still be in conformance with highway law regulating the size of trailers. 
     The storage tank is provided with a sloped bottom wall and a side manhole positioned so that a person, while standing on the ground, can have access to the interior of the tank for the cleaning thereof. 
     The storage tank is also provided with a jack system and a king pin for a fifth wheel on the front thereof, and a rear wheel lift system, to not only facilitate the towing of the empty tanks by a regular tractor, but also to facilitate the draining of the tank, and provide a new method of transporting and draining fluid from the tanks. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a side elevational view of the mobile storage tank of the present invention, with the rear wheels in the lowered position and the front portion of the storage tank resting on the ground; 
     FIG. 2 is an elevational view of the side of the tank opposite to that shown in FIG. 1, and showing the rear wheels in the elevated position and the storage tank resting on the ground; 
     FIG. 3 is a top plan view of the storage tank; 
     FIG. 4 is an enlarged front elevational view of the storage tank; 
     FIG. 5 is a fragmentary, horizontal sectional view taken substantially along line  5 — 5  of FIG. 1; 
     FIG. 6 is a fragmentary, cross-sectional view taken substantially along line  6 — 6  of FIG. 1; 
     FIG. 7 is a rear elevational view of the mobile storage tank wheel chassis in the elevated position; 
     FIG. 8 is a fragmentary, side elevational view of the rear of the storage tank, showing the tank resting on the ground when the rear wheels are in the elevated position; 
     FIG. 9 is a rear elevational view of the mobile storage tank wheel chassis in the lowered position; 
     FIG. 10 is a fragmentary, side elevational view of the storage tank showing the rear of the tank in the elevated position above the ground when the rear wheels are in the lowered position; 
     FIG. 11 is a view taken substantially along line  11 — 11  of FIG. 10 illustrating the extension and retraction mechanism for lowering and raising the rear wheel chassis; 
     FIG. 12 is a side elevational view of one of the latching devices employed in the extension and retraction mechanism shown in FIG. 11; 
     FIGS. 13,  14 ,  15  and  16  are side elevational views illustrating the sequential steps of attaching the mobile storage tank to a tractor for transport; and 
     FIG. 17 is a side elevational view of a pair of tandem mobile storage tanks connected to a tractor. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings in greater detail, and more particularly to FIGS. 1,  2  and  3 , the mobile storage tank of the present invention comprises, an elongated enclosure having a front or forward end  1 , a rear end  2 , a pair of opposed, vertically extending side walls  3  and  4 , a top wall  5 , bottom wall  6  at the rear end, and a bottom wall  7  at the forward end. The bottom walls  6  and  7  are sloped downwardly toward a downwardly curved bottom wall  8  intermediate the bottom walls  6  and  7 , with a rearwardly extending drain fitting  8   a  communicating with the inner bottom of the bottom wall  8 . 
     As will be seen in FIGS. 3,  4  and  5 , a recess  9  is provided in a corner of the tank at the forward end  1  inside wall  3  for accommodating a ladder  10  to facilitate access to the tank top wall  5  and manhole  11  mounted therein. It is to be understood that recess  9  can be provided in any corner of the tank but the forward right corner in which it is shown is the preferred position. The recess is formed by bottom wall  9 ′ extending diagonally between, and connected at its ends to, top wall  5  and external portion  7 ′ of forward bottom wall  7 . The side edges of diagonally extending bottom wall  9 ′ are connected by welding to corresponding diagonal edges of side wall  3  and recessed side wall portion  3 ′. The ladder  10  is connected to the diagonal or downwardly and forwardly sloping bottom wall  9 ′ by stand-off elements  10 ′. 
     Similarly, recesses  12 ,  13  and  14  are provided in the forward end  1 , side wall  3  and rear end  2 ′ for housing manholes  15 ,  16  and fitting  17  (FIGS.  6  and  7 ), respectively. By recessing the ladder  10 , manholes  15  and  16 , and fitting  17  within their respective walls a maximum volumetric dimension can be obtained for the storage tank while still conforming to highway laws regulating the size of trailers. 
     Furthermore, the manholes  15  and  16  are positioned at a predetermined height so that a person, while standing on the ground, when the tank is on the ground, can have access with his head, shoulder and arms to the interior of the tank for the cleaning thereof. The draining and cleaning of the tank is further facilitated by the sloped bottom walls  6  and  7  communicating with the longitudinally extending curved bottom wall  8  which, in turn, communicates at the rear end thereof with a laterally and downwardly extending conduit  18  having a hinged cover  19 . The arcuately curved bottom wall  8  also communicates at the rear end thereof with the rearwardly extending centrally located drain fitting  8   a , and at the front end thereof with the forwardly extending centrally located drain fitting  8   b . These three drains provide the operator versatility in cleaning and draining the tank according to its position relative to where the fluid being drained must be directed. The rearwardly extending drain fitting  8   a  is connected on vertical rear end wall  6 ′ that connects rear sloped bottom wall  6  to curved bottom wall  8 , while forwardly extending drain fitting  8   b  is connected on vertical front end wall  7 ″ that connects forward end sloped bottom wall  7  to curved bottom wall  8 . 
     As will be seen in FIGS. 4 and 6, the curved bottom  8  having the rearwardly extending drain fitting  8   a  and forwardly extending drain fitting  8   b , is supported by cradle members  20  connected between the curved bottom  8  and a flat, reinforced floor  21  constructed of longitudinally and laterally extending channel members, providing a skid for supporting the tank on the ground  22 , as shown in FIGS. 2 and 13. The tank can also be supported on the ground by a pair of laterally spaced, telescopic jacks  23  which can be either manually actuated or fluid actuated, the jacks  23  being connected to the tank adjacent opposite sides and adjacent the rearwardly extending end of sloped bottom wall  7 , and in front of vertical front end wall  7 ″, as shown in FIGS. 1,  2  and  4 . The telescopic jacks  23  have a retracted length such that in the retracted position, as shown in FIGS. 1,  2  and  4 , the top ends are adjacent the bottom of front bottom wall  7 , and the bottom ends are adjacent the bottom of reinforced floor  21  and the ground, thus extending the height of reinforced floor  21  and front end wall  7 ″. A king pin  24  is connected to the bottom wall  7  for connection to the fifth wheel of a tractor to be described more fully hereinafter. 
     Referring to FIGS. 7 to  10 , the rear of the storage tank is supported by a rear wheel chassis  25  including an axle  26  connected to the medial portion of a leaf spring  27  having its outer ends connected to spring hangers or brackets  28  and  29 . While bracket  28  is fixedly connected to the bottom wall  6  of the storage tank, the bracket  29  is mounted to the outer end of a cross beam  30 , as shown in FIG.  11 . 
     A fluid motor  31 , including a cylinder  32  connected to the bottom wall  6  and a piston rod  33  connected to the cross beam  30 , is provided either for raising the cross beam  30  and associated wheel chassis  25 , to thereby lower the storage tank to rest on the ground, as shown in FIG. 8, or for lowering the wheel chassis  25  to lift the storage tank off the ground, as shown in FIGS. 10 and 11. 
     The reciprocatory movement of the cross beam  30  is guided by a pair of spaced, parallel, vertically extending tubes  34  having their lower end portions integral with the cross beam  30 , and their upper end portions telescopically received in tubular members  35  integral with the bottom wall  6  of the storage tank, and protruding through the bottom wall to the inside of the storage tank, as shown in FIGS. 6 and 11. In order to hold the guide tubes  34  in the extended position, while the wheel chassis  25  is in the lowered position, a latch assembly  36  is provided for each telescopic tube  34 . Each latch assembly  36  comprises a plate  37  pivotally connected as at  38 , by a pivot rod welded on one end, to the lower end of movable tube  34 . The free end of plate  37  is provided with an apertured flange  39  having a boss  40 . A similar apertured flange  41  is fixedly attached to the lower end of tubular member  35  by a bracket  42 . To hold the tube  34  in the extended position, the plate  37  is pivoted upwardly, as shown in FIG. 12, so that the boss  40  abuts and aligns with the apertured flange  41 , and a latch pin  43  is inserted through the flange  41 , boss  40 , and flange  39 . 
     FIGS. 13 to  16  illustrate the method by which an empty storage tank is transported from one site to another. As will be seen in FIG. 13, the storage tank is resting on the ground and a tractor  44  is backed into position so that the fifth wheel  45  on the tractor  44  is aligned with the king pin  24  on the storage tank. Suitable pneumatic and/or hydraulic hoses  46  are then connected between the storage tank and the tractor  44  to use the pressurized system on the tractor to pressurize the pneumatic and/or hydraulic system, not shown, on the storage tank. The jacks  23  are then extended, as shown in FIG. 14, to lift the front of the storage tank a sufficient distance to allow the tractor  44  to back into the front of the storage tank to lock the fifth wheel  45  to the king pin  24 , as shown in FIG. 15, while the brakes on the rear wheel chassis are applied. The fluid motor  31  is then actuated to lower the rear wheel chassis  25 , to thereby lift the rear of the storage tank off the ground, as shown in FIG. 16, and the jacks  23  are retracted and the latch assemblies  36  are manipulated, and the latch pins  43  inserted, to hold the wheel chassis  25  in the lowered position. 
     After the tank is transported to its new site it is deposited on the ground at the new site using the reverse method described, except that after the rear wheel chassis is raised to lower the rear end of the storage toward the ground, the jacks  23  are then extended to the ground to support the forward end of the storage tank above the ground. The king pin  24  is then disconnected from the fifth wheel  45  of the tractor  44  by moving the tractor out from under the king pin  24 . The jacks  23  are then retracted lowering the reinforced floor  21  of the storage tank onto the ground. It is to be understood that in this method of lowering the tank onto the ground, the jacks  23  can first be extended into contact with the ground and thereafter the rear wheel chassis can be raised to lower the rear end of the tank, or these steps can be conducted simultaneously, followed by the steps of disconnecting the king pin from the tractor, and then lowering the tank onto the ground by retracting the extended jacks  23 . 
     While one storage tank can be transported, as shown in FIGS. 13 to  16 , a pair, or more, of storage tanks can be transported in tandem, as shown in FIG. 17, wherein the second storage tank is connected to the rear end of the first storage tank by a conventional trailing dolly  47  having a fifth wheel  48  connected to the king pin on the second trailer and a tongue  49  connected to a hitch  50  on the rear of the first trailer. 
     While the manipulation of the jacks  23  and wheel chassis  25  has been described with regard to the connection of the storage tank to a tractor, it will be appreciated by those skilled in the art that the movement of the jacks  23  and wheel chassis  25  can also be employed for tilting the storage tank so that the tank can be fully drained through the fittings  8   a  and  8   b  and the laterally extending conduit  18  during the cleaning of the tank, which cleaning is further facilitated by the manholes  15  and  16  being positioned at a predetermined height above the ground to allow a person standing on the ground to have access to the interior of the tank with his head, shoulders, arms, and a hose for hosing down the interior. 
     The storage tank has a pair of pressurized pneumatic tanks, not shown for sake of clarity, for pressurizing the pneumatic and/or hydraulic systems on the storage tank. These pressurized pneumatic tanks are preferably located above the rear wheel chassis  25 , below rear bottom wall  6 , and between fluid motor  31  and rear end wall  6 ′. This pressurized pneumatic source is connected into the brake system of the rear wheel chassis as a safety feature, and can be used in the new method of cleaning the tank, or the pressurized system of the tractor can be used by connecting the hoses  46  from the tractor to the tank system. Which pressurized source will be used in the cleaning method will depend upon the orientation of the tank at the site relative to a holding pond or the like for the waste cleaning water from the tank, and if a tractor can be placed adjacent the tank. 
     If, for instance, the waste fluid holding pond is in front of the tank, the waste water from cleaning will be drained from the storage tank through forwardly extending drain fitting  8   b . With the tank on the ground using side manhole  16 , and/or front manhole  15 , the cleaner can bend to place his head, shoulders, arms and the nozzle of a cleaning hose inside the tank during a hose-down cleaning operation. Since rear bottom wall  6  and front bottom wall  7  slope downwardly toward the downwardly curved side bottom wall  8 , all of the waste cleaning fluid drains down to the bottom wall  8 . With a drain hose attached to forwardly extending drain fitting  8   b  fluid motor  31  is actuated to lower the rear wheel chassis  25 , as shown in FIG. 1, to thereby lift the rear of the storage tank off the ground, while the front of the storage tank is still on the ground, causing the waste cleaning water to be expelled through forward drain fitting  8   b  which is then at the lowermost point of the storage tank. 
     If, for instance, the waste fluid holding pond is in back of the storage tank, the waste water from cleaning will be drained from the storage tank, in a similar manner, either through rearwardly extending drain fitting  8   a  or side conduit  18  and cover  19 . With the rear wheel chassis  25  raised, and its brakes applied, the pair of jacks  23  are extended to thereby lift the front of the storage tank off the ground to the point as shown in FIG. 14, causing the waste cleaning water to drain to the rear of the tank and be expelled through rearward drain fitting  8   a  and/or side conduit  18  and manhole cover  19 , which are then at the lowermost point of the storage tank. 
     The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.