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FIELD OF THE INVENTION 
     The present invention relates generally to the paving of large surfaces, such as highways and parking lots, and, more particularly, to an extension for a screed that compacts a joint between paving swaths of bituminous concrete. 
     BACKGROUND OF THE INVENTION 
     Large surfaces to be paved require multiple passes of the paving apparatus, including a screed for leveling a layer of bituminous concrete, typically referred to as blacktop. The layer of blacktop along the edge of a paving swath against which a subsequent swath of blacktop is to be laid is typically formed with a joint to facilitate the joinder of the adjacent layers of blacktop. The joint is formed by a screed extension that is shaped into the desired joint configuration. Compaction of the bituminous concrete is accomplished primarily by motorized roller machines passing back and forth over the layer of blacktop previously laid. Motorized roller machines cannot roll over the joint portion of the blacktop layer as the compaction action would destroy the configuration of the joint. 
     Bituminous concrete is typically applied in layers, referred to as courses, with a base layer being deposited over a stone base or other support, followed by a wear course deposited over the top surface of the base course. The blacktop is trucked to a screed that deposits the blacktop in a course having a predetermined thickness. Since the screeds have a discrete width, large surfaces to be covered require two or more passes with the screed laying adjacent swaths of blacktop with each pass. As shown in  FIG. 2 , the wedge notch joint  2  is formed along a side of a swath  1  of blacktop for the merger of the adjacent swaths of blacktop and typically has a configuration specified by contract specifications. The wedge notch joint  2  is typically configured with an upper lip  3  defining an edge having a depth of perhaps one-half inch, the actual depth being determined by the size of aggregate being used in the blacktop being deposited as the height being at least the maximum size of the aggregate. The joint  2  then has a sloped portion  5  that extends from the upper lip  3  downwardly to a lower lip  7  that forms an edge having a height at least as great as the maximum size of the aggregate used in the course of blacktop being deposited in the adjacent swath. 
     This joint configuration provides for a smooth joinder of adjacent swaths of blacktop. Compaction of the joint area is accomplished after the adjacent layer of blacktop is deposited so that the motorized roller machine is run over top of the joinder area. The problem arises with the first swath of blacktop from which the joint is formed cures before the subsequent swath is applied on top of the joint and the motorized roller machines are ineffective to compact the cured joint on the first swath. When compaction tests are performed, the joint area is typically the primary locations at which the compaction tests fail. 
     It would be desirable to provide a screed extension that would be operable to form a joint for the merger of adjacent swaths of a blacktop course in the desired configuration, but with an ability to compact the joint area when the swath on which the joint is formed is deposited, and before the application of the adjacent swath of blacktop. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to overcome the disadvantages of the prior art by providing a screed extension that incorporates a compaction device to compact the joint area of a swath of a course of bituminous concrete. 
     It is another object of this invention to provide a screed extension that is selectively configurable to form a wedge notch joint area for the merger of adjacent swaths of a course of blacktop in multiple configurations. 
     It is a feature of this invention that the screed extension can be used on either the left side or the right side of a conventional screed machine to form a joint area on a swath of blacktop being deposited by the screed. 
     It is an advantage of this invention that the screed extension is selectively configurable to provide a joint area for the merger of adjacent swaths of blacktop on either side of a conventional screed in the desired joint configuration. 
     It is another feature of this invention that the screed extension includes a base plate that is supported on opposing lateral sides by linear actuators that are operable to locate the lateral edges of the base plate at a desired position relative to a frame of the screed extension. 
     It is another advantage of this invention that the selectively positionable base plate can be configured to form a desired wedge notch joint configuration on either side of the screed. 
     It is yet another feature of this invention that the base plate is formed for the mounting of a vibration unit that provides compaction operation for the base plate. 
     It is yet another advantage of this invention that the positionably configurable base plate forms the joint area and also provides compaction of the joint area prior to the application of a subsequent adjacent swath of blacktop. 
     It is still another advantage of this invention that the vibration unit can be powered either electrically or hydraulically. 
     It is a further advantage of this invention that the linear actuators can be powered electrically. 
     It is a further feature of this invention that the vertical positioning of the sides of the base plate is provided through operation of a gear box coupled to the linear actuator. 
     It is a further object of this invention to provide a screed extension for the formation of a wedge notch joint to facilitate the merger of adjacent swaths of a blacktop course, which is which is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use. 
     These and other objects, features and advantages are accomplished according to the instant invention by providing a screed extension selectively connected to opposing sides of a paving screed used to lay a blacktop over large surfaces to create a wedge notch joint for merging with an adjacent swath of blacktop. The screed extension includes a positionable base plate that can be oriented at a selective depth relative to the screed. The base plate is connected to linear actuators through a gear box corresponding to opposing sides of the base plate to position the corresponding side of the base plate at a selected height to orient the base plate in a sloped configuration to form the wedge notch joint along a side of a course of blacktop. The base plate supports a vibration unit providing compaction to the wedge notch joint as the course of blacktop is being deposited, thus providing a dense joint between adjacent swaths of a course of blacktop. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features, and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description that follows, in conjunction with the accompanying sheets of drawings. It is to be expressly understood, however, that the drawings are for illustrative purposes and are not to be construed as defining the limits of the invention. 
         FIG. 1  is a schematic representative perspective view of a screed on which a screed extension incorporating the principles of the instant invention can be mounted, the screed extension being schematically shown on opposing sides of the screed with the positionable base plate being shown in phantom; 
         FIG. 2  is a perspective view of a swath of a course of blacktop having a wedge notch joint formed along one edge thereof, a representative wedge notch joint at the opposing side of the paving swath being shown in phantom; 
         FIG. 3  is a perspective view of the screed extension incorporating the principles of the instant invention, the adjacent portion of the screed on which the screed extension is mounted being representatively shown though broken away for purposes of clarity; 
         FIG. 4  is a front elevational view of the screed extension with the linear actuators and a portion of the base plate broken away to show the movement of the slide plates supporting the base plate for positioning in forming the wedge notch joint, the movement of the base plate and slide plates being shown in phantom; 
         FIG. 5  is an elevational view of a slide plate; 
         FIG. 6  is an end view of the slide plate shown in  FIG. 5  with movement of the lower hinged portion being shown in phantom; 
         FIG. 7  is an elevational view of a side sheet forming part of the frame of the screed extension, the mounting of a slide plate thereon being shown in phantom; 
         FIG. 8  is a side elevational view of the base plate, the connection thereof to a slide plate and the mounting of a vibration unit thereon being shown in phantom; 
         FIG. 9  is a top plan view of the base plate as shown in  FIG. 8 , the mounted vibration unit being shown in phantom; 
         FIG. 10  is a top plan view of the screed extension showing the mounting of the linear actuators to drive the gearboxes shown in phantom, which in turn are connected to the opposing sides of the base plate for positioning the base plate in a selected orientation for forming the wedge notch joint; 
         FIG. 11  is a front elevational view of the mounting plate for the support of the linear actuators and the corresponding gear boxes; 
         FIG. 12  is a side elevational view of the linear actuators mounted on the frame of the screed extension and being drivingly connected to the gearboxes shown in phantom to effect movement of the base plate according to the principles of the instant invention; and 
         FIG. 13  is a side elevational view of the linear actuator. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1-4 , a screed extension incorporating the principles of the instant invention can best be seen. The screed extension  10  is detachably mounted to the side of the paving screed  9  by fasteners  11  that secure the frame  12  of the screed extension  10  in a fixed position relative to the screed  9 . The frame  12  is formed in a manner that the screed extension  10  is selectively mountable to the screed  9  on either side thereof. Thus, the screed extension  10  is operable as described in greater detail below to form a wedge notch joint  2  on either side of the swath  1  of blacktop being deposited to cover a surface. 
     The frame  12  of the screed extension  10  is formed with laterally opposing side sheets  15  that receive the fasteners  11  to secure the adjacent one of the side sheets  15  to the screed  9 . The opposing side sheet  15  can be supported on a mounting arm  8  extending from the screed  9  to rigidly support the frame  12  of the screed extension  10  on the screed  9 . The frame  12  also includes a gear box mounting plate  13  and a front plate  14  that are supported between the opposing side sheets  15  to define the screed extension frame  12 . The screed extension  10  also includes a pair of opposing slide plates  16  formed with an upper portion  17  connected to a lower portion  19  by a hinge  18  allowing the lower portion  19  to pivot relative to the upper portion  17 . The slide plates  16  are mounted in a laterally opposing orientation adjacent each of the respective side sheets  15 . Preferably, the slide plates  16  are mounted on the outboard sides of the corresponding side sheets  15  to control the movement of the lower portions  19 , as will be described in greater detail below. 
     Referring now to  FIGS. 3 ,  4 ,  8  and  9 , a base plate  20  is supported between the side sheets  15  from the lower portions  19  of the slide plates  16 . The base plate  20  includes a flat leveling portion  21  spanning the lateral distance between the slide plates  16 . The leveling portion  21  includes perpendicular mounting tabs  22  on opposing lateral sides thereof for connection of the base plate  20  to the respective lower portions  19  of the slide plates  15 . As is best seen in  FIGS. 4 and 7 , the side sheets  15  are formed with a central cutout  24  that permits the connection of the mounting tabs  22  to the lower portions  19  while the base plate  20  is located between the side sheets  15  and the slide plates  16  are located outboard of the side sheets  15 . Furthermore, the slide plates  16  are oriented with respect to the side sheets  15  such that the hinges  18  are located above the central cutout  24 , when in the upper most position, to limit the movement of the lower portions  19  inboard of the side sheets  15 , as will be described in greater detail below. The base plate  20  also includes a central support member  23  projecting upwardly and outwardly of the leveling portion  21  to provide for the mounting of a vibration unit  29 , shown in phantom in  FIGS. 8 and 9 . 
     As is best seen in  FIGS. 3 ,  4  and  10 - 13 , the gearbox mounting plate  13  is horizontally oriented between the side sheets  15  for the support of a pair of worm gear boxes  25 , each gearbox  25  having a vertically oriented positioning shaft  26  extending above and below the respective gearboxes  25 . Each positioning shaft  26  is connected to the upper portion  17  of a corresponding slide plate  16  by a connecting fastener  27  passing through a vertical slot  28  formed in the side sheet  15  for the passage of the connecting fastener  27  between the positioning shaft  26  and the slide plate  16 . The gearboxes  25  are rotatable independently so that a rotation of each gearbox  25  causes a vertical movement of the positioning shaft  26  which is transferred to the slide plate  16  to move the slide plate  16  vertically relative to the corresponding side sheet  15 . 
     Consequently, the vertical movement of the slide plate  16  is transferred to the mounting tab  22  on the base plate  20  to cause a corresponding side of the base plate  20  to move vertically. Since each gearbox is operable independently, the respective movements of the sides of the base plate  20  will angle the base plate  20  into a desired orientation to form the requisite wedge notch joint  2 . A linear actuator  30  is mounted on the gearbox mounting plate  13  for driving connection to each of the worm gearboxes  25 . Each linear actuator  30  is preferably electrically powered, although the actuators  30  could be hydraulically operated as well. Each linear actuator  30  includes a drive member  31  coupled to the worm gear box to operate the corresponding gear box independently to allow the selective positioning of the base plate  20  in a desired manner for creating the wedge notch joint  2 . 
     In operation, the screed extension  10  is mounted onto the side of the screed  9  on which the formation of a wedge notch joint  2  along the edge of the swath of paving  1  is desired by securing the frame  12  of the screed extension  10  to the side of the screed  9  by the fasteners  11 . Prior to starting the paving operation, the base plate  20  is properly oriented by activating the respective linear actuators  30  to lower the corresponding sides of the base plate  20 . Typically, the side of the base plate  20  closest to the screed  9  will only be positioned downwardly about a half of an inch to form the upper lip  3  relative to the paving swath  1 . The opposing side of the base plate  20  is then lowered sufficiently to orient the base plate  20  at the required angle to form the sloped portion  5 , and to be spaced above the surface being paved a distance of about a half of an inch to form the lower lip  7 . Once the base plate  20  is properly oriented, the blacktop material can be placed into the screed  9  and the screed extension  10  to lay a swath of paving while forming the wedge notch joint  2  with the screed extension  10 . 
     The mounting of the vibration unit  29  on the support member  23  causes the paving material on the sloped portion  5  beneath the base plate  20  to be compacted. The oscillatory vibration exerted by the vibration unit  29  causes the base member to vibrate, which is transmitted to the paving material along the sloped portion  5 . Preferably, elastomeric members  35  are used with the fasteners  11  connecting the screed extension  10  to the side of the screed  9  and to the mounting arm  8  to isolate the vibration within the screed extension  10 . Adjuster screws  37  supported from horizontal portions of the side sheets  15  can be used to define the maximum raised position of the base plate  20 , which in turn defines the depth of the lip  3  in the wedge notch joint  2 . If the screed extension  10  is to be used to simply extend the operative width of the screed  9  without forming the wedge notch joint  2 , the adjuster screws  37  can be raised to position the base plate  20  in alignment with the screed  9 . 
     The movement of the slide plates  16  is best seen in  FIGS. 4-8 . The vertical positioning shaft  26  of the gearboxes  25  is connected to the connecting fastener  27  that passes through the slot  28  formed within the side sheets  15 . Movement of the slide plates  16  is restricted to being vertical in nature by the utilization of guide pins  39  passing through parallel slots  38 . The slide plate  16  is oriented on the corresponding side sheet  15  when in the maximum raised position so that the lower portion  19  is located within the central cutout portion  24 , thus enabling the connection of the mounting tabs  22  of the base plate  20  to the lower portion  19  of the slide plate  16  with the side sheet  15  located inboard of the slide plate  16 . The hinge  18  is located above the central cutout portion  24  behind the side sheet  15 , as is represented in  FIG. 7 , so that the lower portion  19  of the slide plate  16  cannot pivot inwardly when placed into the maximum raised position. 
     When the linear actuator  30  is manipulated to lower the outboard side of the base plate  20 , the hinge  18  lowers into alignment with the central cutout portion  24 , thus clearing the lower portion  19  to pivot inwardly relative to the corresponding side sheet  15 , as is depicted in  FIG. 4 . In this manner, the base plate  20  is capable of angling in an orientation that will form the sloped portion  5  of the wedge notch joint  2  in the desired manner. When both sides of the base plate  20  are moved into the maximum raised position, as shown in solid lines in  FIG. 4 , the base plate  20  cannot pivot on the slide plates  16  as one side sheet  15  prevents movement in one direction and the opposing side sheet  15  prevents movement in the opposite direction. 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiments of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. The invention is not otherwise limited, except for the recitation of the claims set forth below.

Summary:
A screed extension is selectively connected to opposing sides of a paving screed used to lay a blacktop over large surfaces to create a wedge notch joint for merging with an adjacent swath of blacktop. The screed extension includes a positionable base plate that can be oriented at a selective depth relative to the screed. The base plate is connected to linear actuators through a gear box corresponding to opposing sides of the base plate to position the corresponding side of the base plate at a selected height to orient the base plate in a sloped configuration to form the wedge notch joint along a side of a course of blacktop. The base plate supports a vibration unit providing compaction to the wedge notch joint as the course of blacktop is being deposited, thus providing a dense joint between adjacent swaths of a course of blacktop.