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FIELD OF INVENTION 
       [0001]    The present invention relates in general to padding techniques, and in particular to compact padding attachments. 
       BACKGROUND OF INVENTION 
       [0002]    Underground cables and pipelines are typically emplaced by laying the cable or pipeline in a prepared trench and subsequently backfilling the trench. Some cables and pipelines are susceptible to damage from stones, rocks, or other hard objects in the backfill material. For example, optical fiber communications cables are considered particularly susceptible to damage in this manner, as are polymeric or plastic pipelines. Also steel pipes are increasingly provided with protective polymeric coatings, which must be protected from penetration or damage by hard objects. 
         [0003]    Consequently, in the laying of cables and pipelines it is increasingly necessary to backfill the trench with fill material that is free of stones or other hard objects. One way to achieve this is to backfill the trench with sand or other suitable fill (padding) material brought from a remote source of sand or rock-free soil. This approach is expensive and time-consuming. Further, where steel pipe is protectively padded with a layer of sand, the filled trench collects standing water in the porous sand fill, leading to premature corrosion of the pipe. Also, the use of a fill material that is different from the surrounding soil results in a loss of cathodic protection, which leads to premature corrosion of steel pipe. 
         [0004]    The alternative is to screen the excavated material dug from the trench to remove stones and other foreign objects and return the screened material to the trench. Several machines, known as padding machines, have been disclosed in the prior art for this purpose. However, existing padding machines are still relatively large and hence must be operated in conjuction with relatively large earthmoving equipment, such as skiploaders and similar pieces of equipment, which are generally unsuitable for small jobs or restricted worksites. 
       SUMMARY OF INVENTION 
       [0005]    The principles of the present invention are generally embodied in compact, self-contained padding machine attachments suitable for use with a range of different base vehicles including, but not limited to, automobiles, ATVs, skid steers, compact loaders, compact track loaders, multi-terrain loaders, and similar relatively small earth moving machines. Preferably, the given base vehicle, which is the prime mover for a padding attachment, mates with that padding attachment in accordance with the universal quick connect standard SAE J2513, although principles of the present invention are applicable to any one of a number of other base vehicle to padding attachment mating techniques. 
         [0006]    Padding machine attachments embodying the present inventive principles are exceptionally compact and mobile and hence are particularly suitable for soil screening and padding operations in small or restricted jobsites, such as those found in urban areas. Exemplary applications include smaller landscaping work and pipeline/cable burial jobs where the right of away is restricted or the general working area is confined. Furthermore, these padding machine attachments are more efficient than conventional padding machines given that, even with their reduced size and weight, they still maintain good throughput. Finally, padding machine attachments embodying the present inventive principles do not require operator specific training. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1A  is a diagram illustrating a representative compact padding machine attachment and associated compact base vehicle suitable for describing the principles of the present invention; 
           [0009]      FIG. 1B  is a more detailed diagram of the compact padding machine attachment shown in  FIG. 1A , with particular emphasis on the hydraulic subsystems; 
           [0010]      FIG. 2A  is a perspective view of the main assembly of the compact padding machine attachment shown in  FIGS. 1A and 1B ; 
           [0011]      FIG. 2B  is front view of the main assembly of the compact padding machine attachment shown in  FIGS. 1A and 1B ; 
           [0012]      FIG. 2C  is a rear view of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0013]      FIG. 2D  depicts a first side of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0014]      FIG. 2E  depicts a second (opposing) side of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0015]      FIG. 2F  is a side cutaway view taken from the first side of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0016]      FIG. 2G  is a side cutaway view taken from the second side of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0017]      FIG. 2H  is a top view of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0018]      FIG. 2I  is a top cutaway view of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0019]      FIG. 2J  is a front cutaway view of the main assembly of the compact padding machine attachment of  FIGS. 1A and 1B ; 
           [0020]      FIG. 2K  is another top view of the main assembly of the compact padding attachment of  FIGS. 1A and 1B  with the inclined conveyor in place; 
           [0021]      FIG. 2L  is another side view of the main assembly of the compact padding attachment of  FIGS. 1A and 1B  with the inclined conveyor in place; and 
           [0022]      FIGS. 3A and 3B  are detailed partial views of the wire mesh conveyor of  FIG. 1B  with particular emphasis on the positive drive chain mechanism. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The principles of the present invention and their advantages are best understood by referring to the illustrated embodiment depicted in  FIGS. 1-3  of the drawings, in which like numbers designate like parts. Additionally, the following issued patents are incorporated herein by reference for all purposes: U.S. Pat. No. 5,097,610 to Bishop for Compact Padding Machine, issued Mar. 24, 1992; U.S. Pat. No. 5,261,171 to Bishop for Pipeline Padding Machine Attachment For A Vehicle, issued Nov. 16, 1993; U.S. Pat. No. 5,479,726 to Bishop for Compact Padding Machine, issued Jan. 2, 1996; U.S. Pat. No. 5,540,003 to Osadchuk for Padding Machine With Shaker For Separator, issued Jul. 30, 1996; and U.S. Pat. No. 5,741,087 to Osadchuk for Chain Separator For Padding Machine, issued Apr. 21, 1998. 
         [0024]      FIG. 1A  is a perspective drawing of a compact padder attachment  100  embodying the principles of the present invention. In  FIG. 1A , compact padder attachment  100  is shown attached to a small tracked earth moving (base) vehicle  101 , such as a Bobcat T300 compact earth mover. It should be noted however that compact padder attachment  100  can be advantageously utilized with a wide range of different base vehicles, including wheeled compact earth movers, cars, light trucks, ATVs, and the like. 
         [0025]    Generally, compact padder attachment  100  includes a blade  102  and a pair of front wings  103   a - 103   b , which together funnel earth disposed along the side of a trench to a wire mesh inclined elevator  104  that transports earth upwards between sidewalls  105   a - 105   b  towards discharge guide  107 . 
         [0026]    An elevator conveyor, not visible in  FIGS. 1A and 1B , receives padding material falling through inclined wire mesh elevator  104  and carries that padding material to a discharge point above transverse conveyor  106 . The padding material deposited by the elevator conveyor, as well as any padding material falling through the upper part of mesh conveyor  104 , is discharged to a lateral deposit point by transverse conveyor  106 . The deposit point could be a trench being filled during a cable or pipeline padding operation, or could be a surface area, as might be under work during a landscaping operation. 
         [0027]    Larger clusters of earth, rocks, and other unwanted debris are conveyed to discharge guide  107  where they fall through to the ground surface below and away from the trench. As discussed further below, wire mesh elevator  104  also includes a shaker assembly that assists in separating padding material from unwanted debris. 
         [0028]      FIG. 1B  is a more detailed drawing of compact padder attachment  100 , which emphasizes the hydraulic subsystems used to drive the moving portions of compact padder attachment  100 . In particular, a manifold  108  receives driving hydraulic fluid from base vehicle  101  through a set of conventional hydraulic hoses. Hydraulic motor  109 , which is coupled to hydraulic manifold  108  through conventional hydraulic lines, drives wire mesh inclined conveyer  104 . A second hydraulic motor  110 , also operating off of hydraulic manifold  108 , drives the belt of transverse conveyer  106 . Finally, a third hydraulic motor  111  provides for the lateral adjustment of the ends of transverse conveyer  106  using a rack and pinion system described in further detail below. 
         [0029]      FIGS. 2A-2L  are a series of views illustrating the main assembly  200  of compact padder attachment  100 . Specifically, in the views provided in  FIGS. 2A-2L , blade  102 , wire mesh conveyer  104 , as well as the belt of transverse conveyer  106  has been removed such that various underlying structures are visible. 
         [0030]    As shown in  FIG. 2A , main assembly  200  is based on a steel frame including sides  201   a  and  201   b . A pair of back plates  202   a  and  202   b  are provided for attachment to base vehicle  101 . In the preferred embodiment, back plates  202   a  and  202   b  are adapted to provide an interface to an SAE J2513 universal quick-connect standard connector on base vehicle  101 , although other padding machine attachment to base vehicle interfaces may be used in alternate embodiments. A pair of skids  203   a  and  203   b  on frame sides  201   a  and  201   b  allow compact padder attachment  100  to slide along the ground in a relatively smooth fashion and with minimal damage. In  FIG. 2A , transverse conveyor  106  is shown in its folded position, as typically used during storage and transport of compact padder attachment  100 . 
         [0031]      FIG. 2B  provides a front view of main assembly  200 . Generally, wire mesh conveyer  104  and the inclined conveyor rotate around a set of rollers and roller shafts, which also provide a shaker function. As shown in the front view of  FIG. 2B , the set of rollers and roller shafts include front lower roller  204 , central roller  205 , lower roller shaft  206 , upper roller shaft  207 , and upper roller  208 . Hydraulic motor  109  of  FIG. 1B  drives the rotation of upper roller  208  and hence the motion of wire mesh conveyer  104 . 
         [0032]    Front lower roller  204  includes a notch  234  and central roller  205  includes a notch  235 , each adapted to engage a corresponding protrusion on the belt of the elevator conveyor, described in further detail below. Generally, the belt of the inclined conveyor loops around the surfaces of front lower roller  204  and central roller  205 . A rectangular protrusion on the bottom of elevator conveyor belt mates with notches  234  and  235  to minimize lateral belt movement. 
         [0033]      FIG. 2C , which provides a rear view of main assembly  200 , shows the third roller upon which wire mesh conveyer  104  travels, namely, rear lower roller  210 . As visible in this view, rear lower roller  210  rotates around a shaft  211  while upper roller  208  rotates around a shaft  209 . A pair of sprockets  240   a  and  240   b  on shaft  211  of rear lower roller  210  are provided for engaging the positive drive chains of wire mesh conveyor  104 , discussed in detail below. 
         [0034]    With specific respects to upper roller  208 , bracket  212  is provided for supporting hydraulic motor  109  of  FIG. 1B  while a shelf  213  provides a support for hydraulic manifold  108 , also shown in  FIG. 1B . Central roller  205  rotates around a shaft  214 , as shown in  FIG. 2C . 
         [0035]      FIGS. 2D AND 2E  are respective opposing side views of main assembly  200  of compact padder attachment  100 . As shown in  FIGS. 2D AND 2E , front lower roller  204  rotates around a shaft  215  journalized in bearings  216   a  and  216   b . Additionally, shaft  214  for central roller  205  is supported by a set of adjusters  217   a - 217   b . Adjusters  217   a - 217   b  allow for the adjustment of the pressure exerted by central roller  205  and lower front roller  204  onto the inclined conveyor belt (discussed below). Similarly, a pair of adjusters  220   a  and  220   b  allow the pressure exerted on wire mesh conveyer  104  by rear lower roller  210  to be adjusted. In  FIGS. 2D and 2E , transverse conveyor  106  is shown in its operational (unfolded) configuration. 
         [0036]    A shield  218 , supported on shield arm  219 , deflects padding material falling through wire mesh conveyer  104  towards transverse conveyer  106 . 
         [0037]    As mentioned above, the lateral extension of transverse conveyer  106  (to either side) is controllable through a rack and pinion system. This rack and pinion system includes pinion rollers  222   a - 222   b  and pinion gears  223   a - 223   d , as shown in  FIGS. 2D and 2E . As also particularly shown in  FIG. 2E , shaft  209  of upper roller  208  rotates within a set of roller bearings  221 . 
         [0038]      FIGS. 2F and 2G  are respective cross sections of the side views shown in  FIGS. 2D and 2E . In particular, as shown in  FIGS. 2F and 2G , each end of shaft  215  of front lower roller  206  is provided with a sprocket  224   a - 224   b . Each end of lower roller shaft  206  is provided with an offset sprocket  226   a - 226   b  while each end of upper roller shaft  207  is provided with an offset sprocket  227   a - 227   b . Finally, each end of shaft  209  of upper roller  208  is provided with a sprocket  225   a - 225   b.    
         [0039]    Sprockets  226   a - 226   b  and  227   a - 227   b  are “offset” because their center points are not concentric with the center points of corresponding roller shafts  206  and  207 . Consequently, the rotation of sprockets  226   a - 226   b  and  227   a - 227   b  is eccentric, which imparts vibration energy into the mesh of wire mesh conveyor  104  to effectuate shaking. 
         [0040]      FIG. 2H  is a top view of main assembly  200  illustrating a selected number of the structures discussed in detail above.  FIG. 2I  is a top sectional view emphasizing the particular structures of transverse conveyer  106 . (In  FIGS. 2H and 2I , transverse conveyor  106  is shown in the folded configuration.) Additional features of transverse conveyer  106  are shown in the front sectional view provided as  FIG. 2J . 
         [0041]    Transverse conveyer  106 , as shown in  FIG. 2I  with the belt removed, is based on a pair of substantially parallel rails  229   a  and  229   b  and a set of spacers, two of which are shown at  230   a  and  230   b . The belt (not shown) of transverse conveyer  106  moves across a set of rollers, two of which are shown at  231   a  and  231   b , as driven by hydraulic motor  110 . Each rail  229   a  and  229   b  supports a rack, one of which  232   a  is shown in  FIG. 2J . Racks  232  interface with pinion gears  223   a - 223   d  to allow the lateral extension of the ends of transverse conveyer  106  to be adjusted in response to the drive provided by hydraulic motor  111 . The interface between rack  232   a  and pinion gears  223   a  and  223   d  is shown in  FIG. 2J . 
         [0042]    The inclined conveyor belt is shown installed in  FIGS. 2K and 2L , which are respectively alternate top and side views of main assembly  200 . In particular, as shown in  FIG. 2K , elevator belt  236  forms a continuous loop around front lower roller  204  and central roller  205 . Protrusion  237 , extending from inner surface of elevator belt  236 , interfaces with notch  234  on front lower roller  204  and notch  235  on central roller  205 . Advantageously, the interfaces between notches  234  and  235  and protrusion  237  minimize transverse movement of elevator belt  236 . 
         [0043]      FIG. 2L  shows elevator conveyor belt  236  forming a continuous loop around central roller  205 . Adjusters  217   a - 217   b  allow the appropriate amount of tension applied to the continuous loop of elevator conveyor belt  236  around front lower roller  204  and central roller  205  to be controlled. 
         [0044]      FIGS. 3A and 3B  are more detailed partial views of the upper side of wire mesh conveyor  104 . As shown in  FIG. 3A , wire mesh conveyor  104  includes mesh  301  of interconnected steel links, which allow screened padding material to fall through towards the elevator conveyor belt  236  and transverse conveyor  106 , while at the same time forcing larger clusters of earth, rocks, and debris to be carried towards discharge guides  107  of  FIG. 1A . 
         [0045]    The lateral edges of mesh  301  are connected to corresponding positive drive chains  302   a  and  302   b . In particular, positive drive chain  302   a  interfaces with sprocket  224   a  associated with front lower roller  204 , sprocket  225   a  associated with upper roller  208 , offset sprocket  226   a  associated with lower roller shaft  206 , offset sprocket  227   a  associated with upper roller shaft  207 , and sprocket  240   a  associated with rear lower roller  210 , shown in  FIGS. 2C and 2F . Similarly, positive drive chain  302   b  interfaces with sprocket  224   b  associated with front lower roller  204 , sprocket  225   b  associated with upper roller  208 , offset sprocket  226   b  associated with lower roller shaft  206 , offset sprocket  227   b  associated with upper roller shaft  207 , and sprocket  240   b  associated with rear lower roller  210 , shown in  FIGS. 2C and 2G . 
         [0046]      FIG. 3B  illustrates a typical sprocket—drive chain interface, using sprocket  225   b  associated with upper roller  208  and positive drive chain  302   b  as an example. 
         [0047]    Advantageously, in this configuration, only a single hydraulic motor  109  ( FIG. 1A ) is required to drive wire mesh conveyor  104 , as well as the shaker assembly comprised of offset sprockets  226   a - 226   b  and lower roller shaft  208 , and offset sprockets  227   a - 227   b  and upper roller shaft  209 . (This shaker assembly imparts vibrational energy into mesh  301 , which in turn facilitates the soil screening process by breaking up clusters of fine soil and by agitating wet soil.) Advantageously, since sprockets  226   a - 226   b  and  227   a - 227   b  are driven directly by positive drive chains  302   a - 302   b , the dedicated shaker assembly drive motor normally found in conventional padding systems is no longer required. 
         [0048]    As shown in the top view of  FIG. 2H , discharge guide  107  defines an aperture  233  that advantageously directs the rejected materials that do not pass through mesh  301  ( FIG. 3A ) to the ground surface under and between the tracks or tires of base vehicle  101  of  FIG. 1A . Furthermore, discharge guide  107  also protects the front of base vehicle  101  and the local hydraulics from being struck by large debris being discharged from compact padding attachment  100 . 
         [0049]    Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
         [0050]    It is therefore contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.

Summary:
A compact earth filtering machine adapted to engage with a base vehicle includes a frame including a guide structure for guiding earth being screened. A set of rollers is supported by the frame, with each roller associated with a corresponding sprocket. A mesh, forming a continuous loop and supported by the rollers, is provided for elevating and screening earth provided by the guide structure. A drive chain, coupled along an edge of the mesh, is adapted to engage the sprockets associated with the rollers. A driver is provided for rotating a selected one of the rollers and the associated sprocket to thereby cause the mesh to elevate and screen the earth provided by the guide structure. A transverse conveyor supported by the frame transports earth screened by the mesh to a discharge point adjacent to the compact filtering machine.