Abstract:
An apparatus used in pairs, each formed of two components, a spring lift roller assembly, (SLRA) and a pair of spring lift lid rollers, (SLLRs) all of which are attached to a mobile tank lid. The roller assembly is mounted at about the midpoint of the depth of the lid, while one of the spring lift lid rollers is mounted at each of the distal and proximal ends along the sidewall of the lid equally spaced from the spring lift roller assembly. The apparatus&#39;s SLRA is disposed on and confined to a track and moves from a central position in the desired direction, left side or right side, for the lid raising. The lid rollers commence a ride on their own track above the SLRA&#39;s track, during the travel of the roller assembly, and when that assembly has reached its maximum travel point, the bearing plates attached to and forming part of the roller assembly rotate such that the lid now overhanging the tank&#39;s side walls, is in a position to and does rotate around the roller bearing of each roller assembly due to gravity, to open the access to the tank&#39;s content and the lid assumes a generally vertical position, having moved from an original horizontal disposition. Closing of the tank is carried out by a reversal of the process. This roll and lift motion is used for placement of material into the tank, but for dumping, the rear bottom opening or rear located side opening gate is opened by being rotated around the hinges on the end wall having such hinges, such that the total tank can be emptied upon having the front elevated or emptied while at rest in a level position by manual effort.

Description:
FIELD OF THE INVENTION 
     This invention pertains to mobile tanks and the lids that are found on them. Such tanks are used for the temporary storage and transportation of liquids or solids on the highway and under off-road conditions. 
     BACKGROUND OF THE INVENTION 
     Mobile tanks that are used to carry and transport solids or liquids, be it water or agricultural chemicals for field use, or for the carrying away of oil rig drilling mud, are often as long as 35 to 40 feet long by about 102 inches wide, —the maximum permitted under the motor vehicle code of California. These large tanks are of a top open box general configuration and have lids that alone weigh in the range of 700 pounds. As such the opening of these lids for receiving input, and for dumping or mere accessing of content can be a chore. There has been a clear need for an easy and inexpensive means for opening the lids of such large mobile tanks. The invention of this application solves that need. 
     It is one object therefore of this invention to provide a new lid raising and tilting apparatus for mobile tanks. 
     It is a second object to provide an apparatus, used in pairs, that can be manually operated to unseal mobile tank lids, and then tilt them for access or discharge. 
     It is a third object to provide a spring loaded lid retainer that permits easy access to the contents of the tank. 
     It is a fourth object to provide an apparatus that permits the lid of a tank to be easily rotated 90 degrees for total access, but within a confined or limited area. 
     It is another object to provide a tank lid opening means that can be operated by one person. 
     It is still another object to provide an apparatus and process for the rolling, tilting and rotation of the mobile tank lid to either side of the mobile tank. 
     It is yet another object to provide a combined rollable and tiltable mobile tank lid apparatus to permit easy discharge of the tank&#39;s contents. 
     Other objects of the invention will in part be obvious and will in part appear hereinafter. 
     The invention accordingly comprises the apparatus possessing the features properties and the relation of components, as well as the procedural steps involved, which are exemplified in the following detailed disclosure and the scope of the application of which will be indicated in the appended claims. 
     For a fuller understanding of the nature and objects of the invention reference should be made to the following detailed description, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a left perspective end view of the tank lid opening and retention apparatus of this invention showing both portions of the apparatus. 
     FIG. 2 is a front elevational view of one portion of the apparatus attached to a tank lid. 
     FIG. 3 is a left side elevational view of the first component of the invention, prior to installation. 
     FIG. 4 is a right side elevational view of the uninstalled first component. 
     FIG. 5 is a left side perspective view of the first component with one element shown partially cut away. 
     FIG. 6 is an interior elevational view of the component of FIG. 2, which forms one portion of the apparatus of this invention. 
     FIG. 7 is a bottom plan view of this component. 
     FIG. 8 is a zoomed out view showing the tank lid in an inclined elevated position attached to the first component of this invention. 
     FIG. 9 is a view similar to FIG. 8 but from a slightly different vantage point and at a later moment in time, during an opening cycle than FIG.  8 . 
     FIG. 10 is a left side close-up of a part of the first component of the apparatus of FIG. 2 
     FIG. 11 is an end view of the first component of the apparatus of FIG.  2 . 
     FIG. 12 is a right side perspective of the second portion of the apparatus of this invention. 
     FIG. 13 is a left side elevational view of the portion seen in FIG.  12 . 
     FIG. 14 is an end elevational view of a mobile tank with the apparatus of this invention mounted thereto. 
     FIG. 15 is a view similar to FIG. 14 but wherein the lid and the first portion of the apparatus have been moved to the far right side of the tank. 
     FIG. 16 is a left side elevational view of the lid interior and showing the first portion of the apparatus attached thereto. 
     FIG. 17 is a side elevation of a mobile tank&#39;s raised lid being retained by the apparatus of this invention. 
     FIG. 18 is a close-up perspective view of a mobile tank and lid and a tie-down system used in conjunction therewith. 
     FIG. 19 is a time-motion view showing the paths of travel that can be had from the opening of the mobile tank lid of this tank, when the lid moves to either the right or left, i.e., to the left or right side of the tank. 
     FIG. 20 is a close-up elevational view of an alternate version of one component of this invention; namely, the component shown in FIG.  2 . This variant is labeled  114 . 
     FIG. 21 is a side close-up perspective of the component shown in FIG.  20 . 
     FIG. 22 is an perspective view of the forward or non-opening end of the tank employing this invention. 
    
    
     SUMMARY OF THE INVENTION 
     An apparatus formed of two components, both of which are at opposite ends of a mobile tank for the linear movement of a top open box configuration mobile tank&#39;s lid and the subsequent 90 degree tilt thereof to either the left or right side of the tank. A pair of spring lift roller assemblies each attached to the tank lid, ride on the upper track of a dual track system, for the depth of the tank on opposite sides of the tank. Each spring lift roller assembly, operates in conjunction with an opposed pair of spring lift lid rollers, which also roll on a track disposed between the front and the back of the mobile tank. Inner and outer bearing plates are interconnected and together ride in a slot of the spring lift roller assembly (SLRA). These plates are in turn mounted to the lid for rotation on a roller bearing disposed between the inner and outer roller bearing plates. When the pair of bearing plates reach their maximum travel distance within the slot of the SLRA, the lid pivots over the tank&#39;s front or rear wall to about a 90 degree angle to thereby provide access to the tank&#39;s content. Closure involves a reversing operation. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The apparatus  10 , of this invention comprises two components; a spring lift roller assembly hereinafter designated SLRA,  12 , used in conjunction with a pair of opposed spaced spring lift lid rollers,  13 , hereinafter designated SLLR. Two apparatuses are required for the movement and opening of a lid of a mobile or other tank. One apparatus is mounted on each end of such a tank which are generally of a rectangular horizontal cross section. 
     Tanks, of a mobile nature, for which the opening of lids is desired, utilizing the apparatus of this invention are depicted in whole or in part in such figures as  15 ,  17  and  19  and are noted as designator  76 . Typically these tanks  76  are rectangular, and have two sides  78  and two ends  88 , a bottom, not seen, a moveable lid  84 , seen in FIGS.  1 , 18  and  19 , and often  4  wheels or rollers  96 , one per corner, for movement. See also FIG.  14 . 
     The apparatus of this invention is used in pairs, to relocate the lid  84  of a tank such that access can be gained to the interior of the tank or container  76  for further addition to the contents therein. (It should be noted that while the contents are loaded through the top they are dumped through the tailgate at the rear of the tank. The actual time sequence and pattern of movement is shown in FIG. 19, and discussion thereon is set forth infra. 
     Reference is made to FIG. 1 wherein the first component  12 , the SLRA is seen disposed at one end of a channel like dual track system  80  connected to lid  84 . Lid  84  is seen to be in a general horizontal disposition, overhanging the side wall of the tank. One SLLR  13 , can be seen but the second opposed one is hidden from view in this figure. Note the presence of the handgrip  86  on the side edge of the lid  84  for use by a workman. Hinges  90  disposed beneath the track, ie. interposed between the track and the tank allow the tailgate to hinge for quick unloading of the contents of the tank. 
     The discussion now moves to the SLRA  12  seen in front elevation in FIG. 2, and seen in front and rear elevation in FIGS. 3 and 4, and in rear perspective in FIG.  5  and top perspective in FIG.  7 . The SLRA  12  main element is the elongated main roller plate  14 , which has three integrated sections of the same thickness but different lengths. The sections are  14 A, the upper;  14 B, the middle and  14 C the lower section. Reference is made particularly to FIGS. 3 and 4. Section  14 A, is a racetrack shape section of the longest dimension, and which has a slot  52  therein. Section  14 B is a solid plate of slightly less extension and which has therein part of a vertical central slot,  60  for the receipt and passage of the vertically spaced mounting bearing bolts  38 , each of which bolts has a bearing  43  thereon, (see FIG. 8) and which bolts are seen best in FIGS. 5 and 6. These bearings though not seen permit unencumbered vertical movement of the main bearing plate  14  between the spacer plate  22  and the inner roller track plate  30 . 
     The third section is a vertically directed central section  14 C, FIG. 3 and 4. This third section is integral to the second section and contains the lower part of the rounded end vertical slot  60 . The upper end of the rounded end vertical slot  60  can be seen in FIG.  8 . The third section  14 C of the main roller plate  14 , has a preferably arcuate lower end. 
     A pair of bearing plates, the outer bearing plate  16  and the inner bearing plate  20  are spaced horizontally from each other by a bearing,  18  per FIG. 4, and each of said bearing plates is disposed on the exterior opposite face of the SLRA  14 . The spacer plate  22  as seen also in FIG. 8, includes a lower central bore and an upper cradle recess in which are disposed the bearing carrying bearing bolts  38 . 
     A threaded shaft  40  passes through aligned unnumbered throughbores in each roller plate, per FIG. 3. A pair of nuts  44 , per FIG. 4 are mounted on the threaded shaft  40  at two locations, one each abutting the external face of one of the two bearing plates. Sleeve  42  overlays the interior end of the threaded shaft  40  to protect the threads. 
     Reference is now made to FIG. 5, wherein it is seen that the upper section  14 A, includes a central inwardly directed pointer  56  that is disposed in the upper part of the oval element and directed into slot  52 . Element  14 A also has a concave notch  54  therein vertically spaced from the pointer in the lower part of the oval element. 
     The two bearing plates  16 ,  20  are configured differently. The outer bearing plate  16  is generally rectangular, and has an aperture  16 A spaced up slightly from its lower end for the receipt of the threaded shaft  40  as per FIGS. 2 and 4. The inner bearing plate  20  is of the same general dimension, has an aperture  20 A, aligned with aperture  16 A for the shaft  40 , but it has chamfered upper corners, and an inwardly directed top flange  20 F mounted normal to the plane of the plate, disposed toward the outer flange plate. This flange,  20 F, best seen in FIG. 7 serves as a spacer member. As can be seen in various figures, the shaft  40  passes through both plates, and the plates can rotate independently on the shaft. The inner plate also includes a concave recess  20 D, which matches the curvature of section  30 H of the inner roller track plate  30 , to permit the bearing  18 , not seen in FIG. 6 to rest in the notch  54  with plate  20  in position disposed above section  30 H. See FIG. 18 for a depiction of the bearing at rest. 
     Disposed between the two plates is a roller bearing  18 , seen in FIGS. 3,  4  and  5  (in cutaway). This roller bearing  18 , also rides on the threaded shaft  40  within the slot  52 , of section  14 A and is of a cross section slightly smaller than that of the slot  52 . 
     As seen in FIGS. 2 and 8, outer spacer plate  22 , which is a generally rectangular vertically disposed plate, includes a pair of vertically aligned bores  22 A, through which pass a pair of bolts  38 , seen best in FIG. 7, each of which bolts are retained by two washers,  48  and a pair of nuts  26 . Bolts  38  which each carry a bearing are connected to permit the lowermost section of the SLLR, 14 C&#39;s vertical slot  60 , to move relative to the fixed bearings carried by bearing bolts  38 , as per FIGS. 2 and 7 upon the urging of the adjacent coil springs. 
     The discussion now turns to FIG. 5 wherein the inner side of the SLRA  12  is seen. The bolt heads of bolts  38  are seen to pass through suitable apertures in the inner roller plate  30 . The plate  30  is a generally rectangular plate with the longer dimension being in a lateral disposition. The two lower corners are preferably radiused, and the plate  30  includes an upstanding hemi-spherical upper segment  30 H, in the same vertical plane as the balance of the unit, through which one of the bolts  38  for retention of main roller plate  14  passes. 
     The inner roller track plate  30  also includes a pair of spaced bores, not seen, through which pass axle bolts  50  to be retained by nuts  26  without washers. See FIGS. 2,  7 , and  9 . 
     Note from FIGS. 2 and 4, among others, the feet  24  which are mounted at the lower edge of the inner roller track plate  30 , and directed away from the plate and inwardly toward each other as well. Note particularly FIG.  2 . Each foot  24  includes a vertical bore  28  for the mounting of a coil spring  58 . Each spring  58  is placed upon an inverted L shaft  62 , which shaft is simply disposed within the bore  28  at its lower end, while the upper end of the shaft is welded to the roller plate  14 . See the detailed close-up view of FIG. 10, as well as FIG. 2 among others for these elements. 
     As noted in FIG. 5, a pair of laterally spaced V-groove casters  34  having aligned grooves  36  are mounted on spaced axle bolts  50 , which bolts are disposed through the outer roller track plate  32  and the inner such plate  30 , which pair retains these casters  34  in place. The outer roller track plate, is a flat horizontally disposed plate with radiused ends for cosmetic purposes. See also FIGS. 3 and 6. 
     Reference is made to FIG. 7, the bottom plan view, where the spacer washers  46  and  48 , also mounted on the axle bolts  50 , are seen separating the V-groove casters from the two roller track plates on the opposite sides of the casters. The axle bolts  50 , per FIGS. 2 and 8 pass through the inner roller track plate  30  per FIG. 7, and are retained by double nuts  26 . 
     The reader&#39;s attention is now directed to the second component of this invention, the spring lift lid roller or SLLR,  13 , which component is employed in mirror image facing pairs on each end wall of the lid  84 . Thus four of these SLLRs are employed with two of the SLRAs for movement and rotation of lid  84 . While seen in FIGS. 1 and 2, specific reference is made to the close-up views of them in FIGS. 12 and 13. 
     Thus each SLLR  13 , includes an angularly disposed, folded arched elongated U-shaped sheet metal plate  19  having a pair of upper aligned apertures  39 U, and a pair of lower aligned ones  39 L at each respective terminus of the arch. Through the upper aperture passes a mount bolt  29 . This bolt  29  passes through the lid outwardly and is terminated by a lock washer, 31  and nut  35  used in combination. This same combination of a washer and nut but designated  41  and  35  respectively are on the exterior end of the lower bolt  33  which retains the roller  37 . See FIG.  12 . 
     A generally right angle triangular flange  19 F is integrally formed with and extends from the interior arm of the U-shaped plate  19 . The 90° angle thereof is adjacent to the interior terminus of the U-shaped plate&#39;s “U”. A small spacer segment  19 FF extends normally to the flange  19 F and is directed inwardly toward the lid. An aperture  43  at the distal end of flange  19 F is for the attachment of coil spring  17  as per FIGS. 12 and 13. 
     A roller  37 , is carried by a lower bolt  33 , which bolt passes through a lower pair of aligned bores,  39 L, which are also in said U-shaped plate,  19  but distant from the U-end. The threaded end of this bolt  33  carries a nut  35  and a spacer washer  41 . 
     An upstanding teardrop metal segment  15  is welded or otherwise attached to the sidewall of the lid  84 S, per FIG.  12 . On this segment  15 , an eyebolt  27  is attached, directed toward the U-shaped plate  19 &#39;s arch. The coil spring  17 , is attached at one end to the eyebolt  27  and at its other end to the flange  19 F&#39;s aperture  43 . 
     Prior to a discussion on how the  2  SLLRs  13 , on each side wall  84 S and the SLRA  12  cooperate to relocate and tilt the lid  84  of the container  76 , the discussion will first relate to the disposition of the SLLRs and the SLRA. Thus reference to FIG. 12 shows that each SLLR is mounted to one end of the sidewall  84 S of the lid  84 . Thus for any one tank there are  4  SLLRS, two on the opposite extremes of each of the two sidewalls  84  of the lid, with each pair being mounted in a mirror image relationship. A review of FIG. 1 shows one SLLR  13 , depicted positioned relative to an SLRA,  12 . 
     As to mounting, a track  80  seen in FIGS. 1 and 2, as well as in FIGS. 8,  9 ,  10  and  11 , serves as the receiver for the SLRA. The track  80  is a C-shaped channel disposed on the top of each of the sidewalls of the tank end  88 , and it is welded into place such as at weld sites  100 , (FIG. 8) to the container&#39;s end  88 , upper edge, along the length thereof. 
     The C-channel includes an upper surface  80 A, a middle surface,  80 B normal to both the upper and lower surfaces, and a lower surface,  80 C, spaced from and parallel to the upper surface  80 A. The track  80  is closed off by track ends  80 E welded upright to the channel  88  as is seen in FIG.  8 . Attached as by welding, braising or some other suitable means to the interior side of the lower surface  80 C, is an inverted V-extrusion  82 , that runs the length of the channel and is designated the lower track. The upper track of similar material designated  83  is the upper track of the dual track system. These extrusions are best seen in FIGS. 1 and 10. It is this inverted V  82 , that fits into the V-groove caster  34 &#39;s V-groove  36 . Again reference is made to FIG.  10 . 
     The V-groove casters  36  are disposed between the two inner and outer roller plates  32  and  34  of the SLRA as has been noted with respect to FIG.  7 . Thus it is understood that the SLRA  12 , rides via its casters on the V-extrusion between the two track ends  80 E of the channel. 
     The sleeved end  42  of the threaded shaft  40  seen in various figures, is disposed into a central tubular portion  94  of a triangular plate  92  which plate is mounted at the midpoint of the side  84 S of the lid  84 . See FIG.  11 . This is the connection between the SLRA  12 , and the lid  84  for the lateral movement of the lid in conjunction with the moving of the SLLRs  13 ; and then for the ultimate pivoting of the lid  84  when the SLRA reaches the end of the track  80  as per the disposition as depicted in FIG.  8 . The threaded shaft  40  connection to the SLRA passes through the two bearing plates  14 ,  16  as per FIGS. 8 and 9 to retain the roller bearing that rides in the racetrack slot as previously discussed. 
     A contrast of FIGS. 1 and 8 shows the positioning of the SLRA at opposite extremes of the track  80 , while FIGS. 9 and 11 shows the lid  84  pivoted. Reference to the figures also reveals that the component  13  rides on the exterior surface of the upper channel member  80 A of the track  80 . 
     OPERATION 
     Now that the components and the connections thereof have been set out the discussion moves to the opening, movement and ultimate tilting of the lid. A stylized time lapse drawing—without the intervening travel between the sides of the container—illustrates the lid&#39;s rotary action in its entirety, transpiring at both the left and right sides position of the container in FIG.  19 . Of course rotation only transpires at one end at any one time. 
     The reader&#39;s attention is turned to FIGS. 2 and 8, not for the specific location of the lid  84 , but to specifically note the presence of the vertical slot  60 . Note further from FIG. 2, how the bearing plate  16  has its lower end below the racetrack slot, as the roller bearing  18 —seen via the cutaway of FIG. 5, is disposed within the notch  54 . Note also how the lid  84  is in close proximity to the container&#39;s walls upper edges, i.e., closed. 
     Reference is now again made to FIG. 5, wherein the slot  60  is not visible. There is no visibility because, when the lid is in position as for travel or prior to movement, the lid  84  is sealed to the edge of the container and so retained by at least one web tightener. 
     In FIG. 18, such a conventional web tightener  98  is seen mounted to the end wall of the container. A nylon webbing section  102 , passes through a swivel latch  100  which webbing when tight holds the lid to the container. At least one such web tightener is found on each end of the container. When the webbing section  102  is tightened down, the two big coil springs,  58  seen best in FIG. 10, as well as in FIG. 8 and 9, are compressed and the slot  60  can be seen. But when the webbing  102  is released, the coil springs relax, and force the roller bearing out of the notch  54 , into the elongated slot, such that the vertical slot  60  can no longer be seen, because the pins  38  per FIG. 5 have moved upwardly in the vertical slot  60 . 
     Restated, in the at rest position, the pins  38  are toward the bottom of the vertical slot  60  and the slot is visible, while the coil springs  58  are under compression. But when the coil springs relax, the pins  38  rise, and the slot  60  becomes no longer visible. See FIG. 14 and 15 among others. 
     In FIG. 14, the SLRA  12  is seen to have moved from its exact center position, slightly to the right. Note how both SLLR&#39;s  13 &#39;s rollers  37  are still riding along the upper member,  80 A. See also FIG. 1, which is a zoomed in view. Note the disposition of the roller bearing  18  situated between the plates  16  and  20 , in that the three elements are at the far right of the racetrack slot  52 . 
     In FIG. 15, a view at a point in time a few seconds later than the view of FIG. 14, one notes that the lid  84  overhangs the container  76  and that only one of the SLLR rollers  37  is still riding on the top surface of the upper member of the C-channel; namely,  80 A, while one roller  37  is hanging in mid-air. But the V-casters have not as yet hit the track end  80 E. 
     FIG. 8 would be the next point in time if the lid had been moving leftwardly rather than rightwardly as has been noted. However the action that transpires is the same, as if the lid had been moving rightwardly, given the understanding of FIG. 19 which shows that the action to the sides of the container is the same. 
     The casters impact the end  80 E, and one spring  26  hangs out beyond the container. The connection to the lid via threaded shaft  40  between the plates  16 ,  20  now overhangs the side of the container. Gravity comes into play, and so we note how one end of the lid  84  dips down and the other end dips up. Reference is again made to FIG.  19 . The tilting of the lid continues downwardly as can be seen in FIG. 9, and FIG. 11, until the lid assumes a generally vertical position with one end sticking up in the air. The lid is disposed beyond the edge of the container, so that the vertical positioning is readily achievable. 
     An end view, showing the lid  84  absolutely upright on the right side of the container is depicted in FIG.  16 . Note the same relative positioning of the other elements. One spring  26  is shown rightwardly beyond the container. Such positioning is also noted from FIG. 17 wherein the viewer&#39;s vantage point is from on the side of the container with the lid having moved sidewardly and being in the air, as opposed to the viewer being on the end of the container, as in FIG.  16 . 
     Returning momentarily to FIG. 1, wherein two of the trio of hinges  90  are seen. These are present only at one end of the tank and are attached to the underside of the track carrying the lid. These hinges are fixed relative to the track, but move with the bottom opening door to permit the unloading of the tank as when hoisted front end up as is known in the art. Thus dumping of the contents of the tank, without having to use shovels, vessels or other implements—depending on nature of the contents—to remove the stored material can easily be accomplished. On the opposite side, suitable spacers—not seen—may be present instead of the hinges,  90  in order to have uniform spacing of the lid and track from the tank&#39;s upper edge, ie. to keep the lid level. Other means to achieve a level lid are also known. 
     FIG. 22 is present to help emphasize the fact that the invention of this application is used in pairs, at both ends of the apparatus. Thus FIG. 22 is seen to be the head end of a tank employing the instant invention. Note the distinct absence of a pivoting door used for disposal of tank contents upon lifting of the tank onto a real or virtual incline. Of course the track is resent on the forward end and is the same as the track described with respect to the rear end of the tank. 
     It is seen that we have disclosed a tank lid retention and removal apparatus that unseals the lid from a mobile tank when the web tighteners are released. When our apparatus is employed, movement of the lid does not drag across the container top edges, but rather the lid rolls across the top edge of the container until such time as more than half of the lid is extended beyond the tank, either side of the tank. At that time, gravity takes over and the lid rotates about the mounting axis to a vertical position for material placement therein. 
     The SLRA is returned toward the center after the dipped end of the lid is manually raised, to help the lid return to a horizontal disposition, which action is followed by manual urging of the lid horizontally toward the interior of the tank. Once the lid is aligned with the edges of the tank the web tightener and its web can be redeployed. During the movement just described the SLRA will move from the edge  80 E inwardly toward the middle of the track  80 . First one of and then the second of the SLLR&#39;s rollers will roll along the top wall exterior surface  80 A of the channel forming the track. 
     Note again that entry into the tank is had through the lid of this invention, but disposal of the tank&#39;s contents takes place through the gate or door built into the rear of the tank. When full, the tank can be manually evacuated, or be subject of machine assisted evacuation, —vacuum hose—as may be desired. The hinged door is again lowered, sealed and the covered tank is again ready for use. 
     It is seen that one person can readily and quickly move the lid from these mobile tanks, a feat that can NOT be accomplished using prior art lid attachment means, which are usually just a pair or more of hinges. 
     The operation of the invention described above is applicable whether one employs the SLRA  12  described supra, which is less preferred, or that component is replaced by the more preferred SLRA  112  to be discussed infra. In the discussion to follow, parts which are the same as part previously described will retain the earlier used number designations. However, where a part is similar to a previously discussed part in function but not in appearance the two digit reference number will not be retained, instead  100  is added to the designator. Where the part is the same as is employed in the less preferred embodiment earlier discussed, its original numeric designator is retained. 
     The SLRA  112  seen in FIG. 20 is an alternative improved embodiment to the one previously discussed. This SLRA  112  has a main element which also is an elongated main roller plate, designated  114 , and which has three integrated sections of the same thickness but different lengths. The sections are  114 A, the upper;  114 B, the middle and  114 C the lower section. Reference is made particularly to FIGS. 20 and 21. Section  114 A, is a modified racetrack shape section of the longest dimension, and it has a boomerang shaped slot  152  therein. Contrast this shape of the preferred embodiment to the racetrack shape of section  14 A earlier discussed and the slot found therein. While referred to as a boomerang, the slot  152  is a lazy V-shaped slot, with the inclination of each “arm’ of the slot being within the range of 7 to 10 degrees above the horizontal. 
     Section  114 B is a solid plate of slightly less extension and which has therein part of a vertical central slot,  60  for the receipt and passage of the vertically spaced mounting bearing bolts  38 , each of which bolts has a bearing  139  thereon, and which are seen best in FIG.  21 . These bearings,  139  permit unencumbered vertical movement of the main bearing plate  14  between the spacer plate  22  and the inner roller track plate  30 . 
     The third section is a vertically directed central section  114 C, in FIG.  20 . This third section  114 C is integral to the second section and contains the lower part of the rounded end vertical slot  60  and is itself preferably arcuate at the bottom. The upper area of the rounded end vertical slot  60  can also be seen in FIG.  20 . 
     A pair of bearing plates, the outer bearing plate  16  and the inner bearing plate  20  are spaced horizontally from each other by a bearing,  18  per FIG. 21, and each of said bearing plates is disposed on the exterior opposite face of the SLRA  114 . The spacer plate  22  as seen also in FIG. 20, includes a lower central bore and an upper cradle recess in which are disposed the bearing  43  carried by bearing bolts  38 . 
     A threaded shaft  40  passes through aligned throughbores in each roller plate, in the manner per FIG.  4  and is secured by a pair of nuts  44 , as shown for this embodiment in FIG. 21, one each abutting the external face of one of the two bearing plates,  16  and  20 . Sleeve  42  overlays the interior end of the threaded shaft  40  to protect the threads. This sleeved end is connected to triangular plate  92 , preferably by insertion into a tubular receiver attached to said triangular plate, and acts in the same manner as the sleeved end  42  discussed supra with respect to the discussion pertaining to FIG. 11 for the connection to the lid. 
     In all other respects the SLRA designated  112  is the same as component  12 . Thus, for example, the coil spring mounts  62  are still welded on at the top and inserted into apertures in the respective foot to carry a coil spring  58 , to permit the springs  58  to act in a manner to dampen the vertical lift of the plate  114 . 
     The SLRA  112  just described in detail with the boomerang slot  152  is the preferred version of the component. The primary reason is that it is easier to manufacture, thus achieving a cost savings during manufacture. Also by having the lower surface of the slot angled downwardly as shown, gravity aids in the central disposition of the bearing  18 ; and the removal from the less preferred depression opposite the pointer is also more difficult to achieve effort-wise, than is a mere angled travel based upon the boomerang angled geometry of the slot  152  of the more preferred embodiment. 
     FIG. 22 is included herein to help the reader comprehend the fact that the invention is utilized at both ends of the tank. All of the views showing the tank have been of the rear end,  77  (see FIG. 14) where the trap or hinged door is placed. Here at the forward end  101  of the tank, there is no hinged door present, rather only a hitch or other similar means  103  to enable the tank or container  76  to be relocated. 
     It should be pointed out to the reader that tanks of this nature are loaded through the top, but are emptied through the hinged door shown to be in the rear of the tank. Indeed, while the tank depicted in the drawings here has a bottom opening rear door, many manufacturers choose to have the “trap door’, be side opening. The hinge location dictates the mode of opening. Top hinged means bottom opening. Of course appropriate seals are employed to retain the contents. However time need not be spent on the details of the unloading door, since the unloading door forms no part of the instant invention. Typically a roll-off hoist can be utilized to raise the mobile tank&#39;s front end into the air for dumping. Truck mounted roll-off hoists are available in the marketplace from various manufacturers, including the assignee of this application. 
     Since certain changes may be made in the above described apparatuses without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.