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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to highway construction equipment, and in particular to an attachment for a backhoe or other earthmoving machine for shaping a trench and/or plowing a base or paving material to a uniform depth. 
     2. Description of the Prior Developments 
     Various attachments have been available for forming trenches and ditches in connection with the construction and maintenance of roads and highways. Although these attachments perform satisfactorily in general, they are not particularly well suited for maintaining a uniform trench depth and width. Moreover, such attachments typically do not control the lateral movement of earth and other material as a ditch is being formed, and such attachments do not have the capability of accurately spreading a level layer of material within or above the surrounding road surface while maintaining clean sides for subsequent compaction by a roller. 
     Accordingly, a need exists for a trench forming apparatus which is of a relatively simple design, yet which can accurately maintain the relative depth of a trench within close limits. 
     A further need exists for such an apparatus which can direct plowed earth and material laterally inwardly toward a trench or laterally outwardly away from the trench as the height of the ditch is being plowed and conditioned. 
     Still a further need exists for such a trenching apparatus which has a vertically adjustable blade for accurately adjusting the height of a trench. 
     Yet a further need exists for a trench or road working apparatus which can level a trench at a height below the surrounding road surface, as well as spread material such as blacktop at a level above the surrounding road surface. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed to fulfill the needs noted above and therefore has as an object the provision of a trench leveling and conditioning apparatus having a generally simple design yet which can accurately maintain the depth of a trench within close limits. 
     A further object of the invention is the provision of a trench conditioning apparatus which can be easily attached to a power machine such as a backhoe or wheel loader and which can control the placement of material moved along the trench. 
     Yet a further object of the invention is the provision of a trench conditioning apparatus having a central height-adjustable blade for setting a trench depth and a pair of adjustable side blades for controlling placement of earth and material located along the sides of a trench and for keeping the earth and material away from the wheels and skids of the apparatus. 
     A further object of the invention is to provide a trench and road conditioning apparatus which has a height adjustable blade for forming a level trench surface below the surrounding road surface, or spreading a level layer of road material at a height above the surrounding road surface. 
     These and other objects are met by the present invention which is directed to a trench conditioning apparatus having a pair of slotted side walls adapted to receive the bucket of a power machine such as a backhoe or wheel loader. A vertically adjustable central blade is supported between the side walls, and a pair of pivoting adjustable side blades is mounted to the side walls on opposite sides of the central blade. 
     The side blades can be pivoted in front of the central blade to laterally direct and plow earth and material into the path of the central blade, or pivoted in back of the central blade to laterally direct and plow earth and material away from the trench and the central blade. In either case, the side blades keep the existing paved edges of the road surface adjacent the trench clean and free of earth and material and thereby provide a clean surface over which the casters and skids of the apparatus and the wheels of the machine used to push it can move. This helps to keep the central blade level insofar as material passing under the wheels of the apparatus and machine used to push the apparatus tends to lift the central blade out of level alignment with the trench. 
     The invention can be used with trenches in virtually any condition, but is particularly adapted for use in trenches which have already been backfilled and compacted. When the trenching apparatus is then moved along such a preconditioned trench, an extremely smooth trench having an accurately selected height can be produced. 
     If desired, the central blade can be raised higher than the side blades and higher than the adjacent pavement over which the side blades ride. In this raised blade position, the trenching apparatus can be used to spread materials such as aggregates and/or blacktop at any desired height, even a height higher than the existing road to allow for subsequent height compaction when the aggregates and/or blacktop are rolled and compressed by a steamroller or other compaction machine. The range of height is from 14″ below the road to 3″ above the road. 
     The aforementioned objects, features and advantages of the invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawings, which form an integral part thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a schematic perspective view of a trench or road conditioning apparatus constructed in accordance with the invention; 
     FIG. 2 is a front view of the apparatus of FIG. 1 with the side blades removed and showing the exploded assembly of one of the side blades on the apparatus; 
     FIG. 3 is a top plan view of the apparatus of FIG. 2, with one side blade positioned in a rearward position and one side blade positioned in a forward position; 
     FIG. 4 is a front view of a caster assembly adapted for use with the invention; 
     FIG. 5 is a front view of a side blade adjusting bar; 
     FIG. 6 is a side view of one of the side blades showing an inside support rib on which half hinges are mounted, and 
     FIG. 7 is a side view of the apparatus of FIG.  1 . 
    
    
     In the various figures of the drawings, like reference characters designate like or similar parts. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described in conjunction with the drawings, beginning with FIG. 1 which shows a road and trench conditioning apparatus  10  constructed in accordance with the invention. The apparatus  10  is designed to condition and level trenches formed in, for example, paved roads as well as to form a level surface on a layer of material extending below or above the road or other surface located laterally adjacent the apparatus. 
     Apparatus  10  includes a pair of parallel side walls  12 ,  14  which extend vertically and longitudinally fore and aft along the length of a trench or road surface. A rearwardly facing open slot  16  is formed in the rear face  18  of each side wall for receiving the bottom edge of a bucket or other similar shaped tool mounted on a power machine such as a backhoe or wheel loader. In this manner, the apparatus  10  can be lifted, propelled and maneuvered over a road or other surface to be conditioned by the apparatus. 
     Although wheels  20  are shown mounted along the lower edge  22  of each side wall  12 ,  14  in FIG. 1, the wheels can be replaced with skids, casters or other ground contact members as discussed below. The side walls  12 ,  14  are interconnected by several cross braces  24 , one of which is shown welded between the front end portions  26  of each side wall  12 ,  14 . 
     A central grading or leveling blade  30  is also mounted between the front end portions  26  of the side walls. The central blade  30  has a replaceable rectangular cutting edge blade  32  bolted to the bottom portion  34  of blade  30 . Blade  30 , as well as side walls  12 ,  14  can be formed of one inch thick steel plate to withstand the high loads experienced in trenching, paving and other road construction operations. The central blade  30  can be dimensioned as a rectangular or square plate. In one embodiment, the central blade is dimensioned as a square having 35 inch sides and the reversible cutting edge  32  is formed of ⅝ inch thick hardened steel plate, 6 inches wide and 34 inches long. 
     As further seen in FIG. 1, one or more rollers  36  are rotatably mounted on each cross brace  24  to support and position the central blade  30  in a fore and aft or longitudinal position. The central blade is provided with a pair of guide bars or guide members  38  which may be welded or otherwise rigidly fastened along the opposed, generally vertical side edges  40 ,  42  of the central blade  30 . The guide members  38  may be formed of rigid steel plates having a flat outer surface  44  closely spaced apart from the inner flat wall surfaces  46 ,  48  of the front portion  26  of the side walls  12 ,  14 . 
     The guide members  38  help to keep the central blade  30  centered in a trench such as a trench cut through a blacktop paved road surface. In addition, the guide members  38  add strength and rigidity to the central blade  30 . It is also possible to dimension the guide members  38  to have planar sliding contact between the guide members  38  and the side walls  12 ,  14  to help to maintain the central blade  30  and plow blade  32  perpendicular to the longitudinal movement of the apparatus  10  along a trench or road surface. The guide members  38  are preferably affixed to project forwardly from and perpendicular to the front face  50  of the central blade  30  and may also extend and project rearwardly and perpendicularly with respect to the rear surface of the central blade  30 . 
     The height of the central blade  30  may be adjusted vertically above or below the level of the surrounding road surface or other surface being worked. In the example of FIG. 1, this surface would be that over which wheels  20  roll. A jack screw, discussed further below, is operated with a crank  52  to raise and lower the central blade  30  in the direction of arrows  54 . In addition, the slight inclination of the central blade  30  can be adjusted as shown by directional arrow  56  as further discussed below. 
     Apparatus  10  is further provided with one or a pair of side blades  60 ,  62  which are pivotally mounted on hinges  64 ,  66  to the front edges  68 ,  70  of one or each side wall  12 ,  14 . Each side blade  60 ,  62  is provided with a reversible cutting edge or scraper blade  72  which may be removably and replacably mounted on the lower edge of each side blade with fasteners such as bolts  74 . 
     Each side blade  60 ,  62  may be adjusted to a position in front of the central blade  30  and in front of the front edges  68 ,  70  of the side walls  12 ,  14 . As shown in FIG. 1, this adjustment is provided by using a telescoping adjustment bar  78 . Bar  78  includes an inner solid rod  80  which slides within an outer tubular rod or sleeve  82 . The inner rod  80  is pivotally pinned to the outer surface  84  of the side wall  12  at pivot joint or hinge  86 . 
     Mounting brackets  87  may be welded to the side walls to receive and support a pivot pin for pinning the hinge  86  to the side wall. The sleeve  82  is similarly pivotally pinned to the rear surface  88  of one or each side blade  60 ,  62  at a pivot joint or hinge  90 . A removable pin  92  is used to adjust the length of the adjustment bar  78  by sliding into aligned bores formed through rod  80  and sleeve  82 . 
     Additional details of the invention are seen in FIGS. 2 and 3. In these figures, the front wheels  20  of FIG. 1 are mounted to the side walls  12 ,  14  by cantilevered steel beams  94  which are welded and/or bolted to the side walls  12 ,  14 . Alternatively, a caster assembly  96 , such as shown in FIG. 4, can be used in place of the beam  94  and wheels  20 . A skid plate  100  can alternatively be used in place of the rear wheels  20  as further seen in FIGS. 3 and 7. Each skid plate  100  is connected to each respective side wall  12 ,  14  with a steel bracket  101 . The caster wheels  98  are connected to the side walls by a welded steel bracket  102  which is bolted in place on the side walls. 
     As further seen in FIG. 2, the side blade  62  is pinned to the half hinges  66  on side wall  14  by a pair of pivot pins  104 . As seen in FIG. 6, the side blade  62  is reinforced with a pair of vertical steel ribs  106  welded to the rear surface  108  of side blade  62 . An angled mounting bar  110  may also be provided on the rear surface  108  of the side blade  62 . Bar  110  acts as an anchoring and strengthening surface into which bolts  74  may be threaded so as to clamp the plow blade  72  to the lower surface of the side blade  62 . 
     While the central blade  30  is of a generally flat planar profile, the side blades  62  are advantageously curved or arcuate in side profile as seen in FIG.  6 . One or both side blades  62  can be quickly and easily mounted or removed from the apparatus  10  by simple insertion or removal of pins  104  into or out of hinges  62 ,  66 . A tubular hinge  112 , as seen in FIGS. 2 and 3, is mounted by, for example, welding to the lower rear surface  108  of side blade  62  to form a pinned pivotal connection with the hinge  90  on the sleeve  82  of the adjustment bar  78 . 
     As noted above, the central blade  30  is supported by a series of rollers  36  which contact the front face  50  of the central blade. These rollers, which are mounted on the front cross brace  24 , hold the central blade against forward movement. The cross brace  24  may be a structural steel plate welded to and between the side walls  12 ,  14 . Roller shafts  114  are mounted across recesses  116  cut in the rear edge of cross brace  24  to receive and support the rollers on the cross brace. 
     Two rear cross braces are mounted behind the central blade  30  as seen in dashed lines in FIGS. 2 and 7. A top rear cross brace  118 , similar to cross brace  24 , is welded or otherwise connected across and to the top portion of side walls  12 ,  14  and a similar lower or bottom rear cross brace  120  is welded or otherwise connected across and to the bottom portion of side walls  12 ,  14 . One, and preferably two, three or more rollers  36  are mounted in a coaxially-spaced series across the front edge of the top and bottom rear cross braces  118 ,  120 . 
     While the rollers  36  on the bottom rear cross brace  120  are preferably fixed in position against the rear surface  122  of the central blade  30  and mounted directly to the bottom rear cross brace on shafts  124 , the rollers  36  on the top rear cross brace  118  are longitudinally adjustable back and forth to provide for an adjustment in the for and aft inclination of the central blade  30  and to adjust the fit and pinch on the central blade between all of the rollers  36  on each cross brace. This adjustment is provided by a pair of adjustable mounting plates  126 . Each mounting plate  126  includes a longitudinal slot  128  which allows each mounting plate to slide forward and backward on top of the top rear cross brace  118 . Fasteners such as bolts  132  may be loosened and tightened as desired to allow the mounting plates  126  to be moved and locked in position as desired. 
     It can be appreciated that the central blade  30  is securely captured between the rollers  36  on the front central brace  24 , and the rollers  36  on the top and bottom rear cross braces  118 ,  120 . The rollers  36  not only support and fix the central blade at a desired inclination, they also allow the central blade to be easily rolled up and down against the rollers to adjust the height of the plow blade  32  either below, at or above the surrounding road surface. 
     This vertical adjustment is provided with a threaded jack screw  134  attached to the crank handle  52 . The jack screw  134  is axially fixed in a rotatable bearing  136  mounted on the top rear cross brace  118 . The lower threaded end of the jack screw  134  is threaded into a threaded bore formed in a steel plate  140  welded to the upper central portion of the rear surface  122  of the central blade  30 . Plate  140  is preferably located between the top and bottom cross braces  118 ,  120 . 
     When the crank handle  52  is turned one way or another, the central blade  30  is raised or lowered independently of the side blades  60 ,  62 . When the central blade  30  is lowered below the side blades, the apparatus  10  acts as a trench leveler or spreader, and when the central blade is raised above the side blades the apparatus  10  acts as a spreader. 
     As seen in FIG. 3, the side blade  60  is adjusted to a position in back of the central blade  30  so as to plow earth or other road materials laterally outwardly away from the central blade. The other side blade  62  is adjusted to a position in front of the central blade  30  so as to plow earth or other road materials laterally inward toward the central blade. Of course, both side blades  60 ,  62  may be adjusted forwardly or rearwardly as desired, depending on the desired operation. In either case, earth and material is cleared from the path of the wheels, casters and skids. 
     The lower edges of the scraper blades  72  on the side blades  60 ,  62  typically scrape over the adjacent surfaces of a paved road as the plow blade  32  on the central blade  30  levels a recessed trench dug beneath the adjacent paved road surfaces. This keeps the adjacent paved road surfaces clean. Alternatively, the central blade can be raised above the adjacent paved road surfaces to level a layer of aggregate or blacktop above these adjacent surfaces. In this case, the scraper blades also keep the adjacent road surfaces free of the aggregate, blacktop or other material being spread and leveled. 
     There has been disclosed heretofore the best embodiment of the invention recently contemplated. However, it is to be understood that the various changes and modifications may be made thereto without departing from the spirit of the invention.

Summary:
A trench leveling blade is movably mounted between a pair of side walls which are slotted to receive the bucket of a backhoe or other excavating machine. The blade is vertically adjustable with a hand operated jack screw. Rollers mounted in front and back of the blade support the blade during use and guide the blade during its vertical adjustment. A pair of adjustable scraper blades is provided on opposite sides of the leveling blade to clean the surface of the pavement adjoining the trench or any other surface being worked by the leveling blade.