Vibratory screed including a spreading device for leveling and distributing plastic concrete in front of the screed
This is a Continuation-in-Part application of U.S. patent application Ser. No. 598,662, filed Apr. 10, 1984, now abandoned, which is a Continuation patent application of Ser. No. 457,727 filed on Jan. 13, 1983, now U.S. Pat. No. 4,466,757. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to vibratory concrete screeds, and more particularly, to vibratory concrete screeds which include a laterally translatable concrete spreading device positioned in front of the screed blade to partially level and distribute plastic concrete before the screed blade engages the concrete. 
     2. Description of the Prior Art 
     The relevant prior art is identified in U.S. Pat. No. 4,466,757 issued on Aug. 21, 1984, the disclosure of which is hereby incorporated by reference. 
     SUMMARY OF THE INVENTION 
     U.S. Pat. No. 4,466,757 discloses a preferred embodiment of the invention including grading means in the form of a rotating auger. In that embodiment of the invention, the partially levelled, redistributed plastic concrete exits the trailing edge of the auger and is immediately intercepted by the advancing front blade of the screed. One improvement of that invention is disclosed and claimed herein and includes metering means which forms a part of the grading means of the present invention. The metering means receives the partially levelled plastic concrete from the distributing means which forms the initial portion of the grading means. The metering means functions to regulate the height of the charge of plastic concrete discharged from the concrete spreading means and intercepted by the screed blade. This improved grading means including both distributing means and metering means sequentially operates on the unfinished plastic concrete to feed a partially finished, constant height charge of concrete to the screed blade as the carriage means of the present invention translates the grading means in first and second directions along the length of the screed frame. 
     U.S. Pat. No. 4,466,757 also discloses an oscillating strike-off concrete finishing mechanism which is coupled to a screed frame in front of the front screed blade. The oscillating strike-off is either coupled between the concrete spreading means and the front screed blade and operates as an intermediate finishing device or may be coupled in a similar position to a screed which does not include concrete spreading means. The improved oscillating strike-off disclosed herein includes means for adjusting the vertical spacing between the oscillating strike-off blade and the screed blade. When used as a concrete finishing device without the concrete spreading means of the present invention, a plurality of spaced apart pneumatic vibrators may be mounted directly on the oscillating strike-off blade to improve the concrete finishing capabilities. 
     The improved invention disclosed herein also includes a paving train consisting of a primary finishing screed including concrete spreading means followed in spaced apart relationship by a secondary finishing screed including an oscillating strike-off. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The invention is pointed out with particularity in the appended claims. However, other objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein: 
     FIGS. 1-30 are included in U.S. Pat. No. 4,466,757 and relate to earlier embodiments of the present invention. 
     FIGS. 31A-D illustrate the excessive build-up of plastic concrete on the blade of a vibrating screed which receives an excessive charge height of plastic concrete. 
     FIG. 32 is a view from above of the blade spill-over problem illustrated in FIG. 31. 
     FIG. 33 is a view from above illustrating the metering means of the present invention coupled to the concrete spreading means. 
     FIG. 34 illustrates the relative position of the metering means of the present invention with respect to the front screed blade and the distributing means of the present invention. 
     FIG. 35 depicts the grading means detached from the carriage means of the present invention to illustrate structure permitting relative vertical adjustment between the grading means and the carriage means. 
     FIG. 36 illustrates the grading means of the present invention including both distributing means and metering means and its relative position with respect to a front screed blade having both forward and rear facing blade sections. 
     FIG. 37 illustrates the grading means of the present invention including both distributing means and metering means with an oscillating strike-off positioned between the grading means and the screed blade. 
     FIG. 38 illustrates the improved oscillating strike-off including vertical strike-off blade adjustment means and a plurality of pneumatic vibrators coupled to the strike-off blade. 
     FIG. 39 is a sectional view of the oscillating strike-off support structure depicted in FIG. 38, taken along section line 39--39, particularly illustrating the structure which couples the oscillating strike-off blade to the screed. 
     FIG. 40 represents a sectional view of the oscillating strike-off illustrated in FIG. 38, particularly depicting the roller structure which maintains a predetermined fixed spacing between the oscillating strike-off blade and the screed blade. 
     FIG. 41 depicts a paver train comprising a primary finishing screed including concrete spreading means followed in spaced apart relationship by a secondary finishing screed including an oscillating strike-off system. 
     FIG. 42 represents a view from above of the paver train depicted in FIG. 41. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In order to better illustrate the advantages of the invention and its contributions of the art, a preferred hardware embodiment of the invention will now be described in detail. 
     The preferred embodiment of the initial version of the invention is fully disclosed in U.S. Pat. No. 4,466,757 which is hereby incorporated by reference. In certain circumstances, that initial embodiment of the invention encountered blade spill over problems of the type illustrated in FIGS. 31 and 32. In the embodiment of the invention as illustrated in FIGS. 1 and 17, the trailing edge of auger 84 was immovably secured to carriage 76 precluding relative vertical adjustments between the trailing edge of auger 84 and front screed blade 16. As the screed advanced forward into an area of unfinished plastic concrete, concrete could spill over the top of screed blade 16 disturbing the finished concrete surface designated by reference number 300 as illustrated in FIG. 31D. 
     In order to overcome this problem, the structure illustrated in FIGS. 33-35 has been created. The grading means 302 of the present invention has now been improved to incorporate distributing means and metering means. In the depicted preferred embodiment of the invention, the distributing means takes the form of an auger 304 and the metering means takes the form of a plow 306. Plow 306 includes a horizontally oriented, continuous lower surface 308 joining together a pair of wedge-shaped end sections 310 which each include a vertically oriented cutting edge 312. Plow 306 is coupled to the horizontally oriented lower surface of chain box 314 which houses the drive chain coupling auger drive motor 92 to auger 304. 
     To optimize operation of the metering means of the present invention, vertical adjustment means is provided to permit precise adjustment of the spacing between the lower surface 308 of plow 306 and the horizontally oriented surface 316 of front screed blade 16. The inner face 318 of auger support bracket 320 includes four spaced-apart, vertically oriented oval apertures 322 which may be mated with either an upper group 324 or a lower group 326 of apertures in the face of auger carriage 76. A set of four bolts (not shown) are inserted through vertically oriented channels 328, through each of the oval apertures 322 and into either the upper or lower group of apertures 324 or 326 as necessary to achieve the desired spacing between the lower surface 308 of plow 306 and the upper surface 316 of front screed blade 316. When the appropriate vertical spacing has been achieved, each of the four spaced apart mounting bolts is tightened to maintain auger support bracket 320, auger 304 and plow 306 in the desired vertical position. For example, for low slump concrete including one and one-half inch stones, the spacing between the lower surface 308 of plow 306 and the upper surface 316 of blade 16 might be adjusted to approximately one and one-fourth inches. For higher slump concrete, the distance between the plow and the screed blade is typically decreased. The particular plow/screed blade vertical spacing which optimizes performance of the present invention with any particular type of plastic concrete can be readily determined by persons of ordinary skill in the art. 
     In operation, the metering means of the present invention, including both plow 306 and the above-described vertical adjustment means, is translated back and forth along the length of the screed and as illustrated in FIGS. 33 and 34 intercepts and moves plastic concrete forward into the trailing edge of auger 304. The rotating blade of auger 304 intercepts and moves the plastic concrete forward and laterally redistributes it to produce a substantially level surface. In addition, the metering means of the present invention regulates the charge height of plastic concrete fed to the advancing screed blade 16 by stripping off and moving forward excess height plastic concrete into the trailing edge of auger 304. The elevation of the lower surface 308 of plow 306 determines the charge height of the plastic concrete fed to screed blade 16. The interrelated operation of the distributing means and metering means of the present invention feeds a partially finished, constant height charge of concrete to screed blade 16 as the carriage 76 translates the grading means of the present invention back and forth along the length of the screed frame as the screed simultaneously advances into the unfinished plastic concrete. 
     FIG. 34 depicts the concrete spreading means of the present invention operating in connection with a single forward-facing screed blade 16. As indicated, the spacing between the lower surface 308 of plow 306 and the upper surface 316 of screed blade 16 may be made quite small. In FIG. 36, screed blade 16 includes both forward facing and rear facing L-shaped blade elements while the spacing between the lower surface 308 of plow 306 and the upper surface 316 of blade 16 has been increased to a distance slightly less than the concrete stone size. The rear edge of plow 306 is situated approximately halfway between the front and rear edges of the front L-shaped section of screed blade 16. In FIG. 37, screed blade 16 includes only a single, rear facing L-shaped blade section and an oscillating strike-off 330 has been coupled to the screed frame between the rear surface of plow 306 and the front surface of screed blade 16. In the particular embodiment illustrated in FIG. 37, the lower blade surface of oscillating strike-off 330 is positioned slightly above the lower surface of screed blade 16 and approximately even with the lower surface 308 of plow 306. In operation, the laterally reciprocating motion of oscillating strike-off 330 accomplishes an intermediate consolidating and finishing operation on the partially finished plastic concrete discharged from the trailing edge of the grading means of the present invention before the plastic concrete is intercepted by screed blade 16. The differential elevation between the lower surface of oscillating strike-off blade 330 and the lower surface of screed blade 16 may be controlled to regulate the height of the charge of plastic concrete fed to screed blade 16. In practice, the lower surface of the blade of oscillating strike-off 330 will typically be adjusted to be even with the lower surface of screed blade 16 or as high as approximately 3/8 of an inch above the lower surface of screed blade 16. Proper adjustment of the oscillating strike-off 330/screed blade 16 height differential can be regulated by a person of ordinary skill in the art to achieve the desired concrete finishing characteristics. 
     Referring now to FIGS. 38-40, screed 332 includes an oscillating strike-off 330 having both a plurality of pneumatically powered, high frequency air vibrators 334 as well as vertical blade adjustment means 336 for controlling the height differential between the lower surface 338 of the oscillating strike-off 330 and the lower surface of screed blade 16. FIGS. 38 and 39 illustrate the structure of vertical blade adjustment means 336. 
     A plurality of vertically oriented brackets 340 are coupled to the vertically oriented face of screed blade 16 and include a centrally located, vertically oriented oval aperture 342 for accommodating vertical adjustments of oscillating strike-off blade support units 344. A bolt 346 extends through the various elements of support unit 344 and is secured to a vertical adjustment clamp 348 which interfaces with the rear surface of bracket 340. When bolt 346 is loosened, the rotation of bolt 350 regulates the vertical position of strike-off support unit 344 with respect to bracket 340 to control the relative elevation of the lower surface 338 of oscillating strike-off unit 330 with respect to the lower surface of screed blade 316. 
     As illustrated by FIGS. 38 and 40, a plurality of spaced apart rollers 352 are coupled by brackets 354 to the interior face of the blade of oscillating strike-off 330. The comparatively long rolling interface between rollers 352 and the vertical face of screed blade 16 maintains the blade of oscillating strike-off 330 parallel to the vertical face of screed blade 16 as the screed is advanced into the unfinished plastic concrete. 
     Continuous, reciprocating motion of the oscillating strike-off 330 is provided by reciprocating means in the form of a dual-action pneumatic ram 356 and the associated connecting linkage 358 depicted in FIG. 38. As illustrated in FIG. 4 of U.S. Pat. No. 4,466,757, oscillating strike-off 330 may also be driven by reciprocating means in the form of hydraulic motor 64 and the associated reciprocation linkage depicted. 
     When the oscillating strike-off 330 is operated without the concrete spreading means of the present invention as depicted in FIG. 38, single or dual paired air vibrators 334 may be coupled as shown to vibrate the blade of the oscillating strike-off. When the oscillating strike-off 330 is configured as indicated in FIG. 37 and positioned between the trailing edge of plow 306 and screed blade 16, the air vibrators 334 will typically be removed to minimize the space occupied by strike-off 330. 
     Referring now to FIGS. 41 and 42, a paving train consisting of a primary finishing screed 360 and a secondary finishing screed 366. Screed 360 includes concrete spreading means 362 while screed 366 includes oscillating strike-off 370. Screed 366 trails screed 360 by a predetermined time or distance to allow the partially finished concrete existing screed 360 to reach a semi-equilibrium condition prior to engagement by screed 366. Screed to screed spacing on the order of twenty to forty feet is typical although other spacing variations would be apparent to one of ordinary skill in the art. 
     It has been found that use of the disclosed two-unit paving train incorporating primary and secondary screeds including concrete spreading means 362 and oscillating strike-off 370 produces a superior concrete finish. Since screeds 360 and 366 typically include precisely controllable, hydraulically actuated winches, the screed translation velocity and screed to screed spacing can easily be regulated. 
     It will be apparent to those skilled in the art that the disclosed vibratory concrete screed and paver train system may be modified in numerous ways and may assume many embodiments other than the preferred forms specifically set out and described above. For example, various different plow configurations other than the disclosed configuration would function effectively as metering means. Distributing means such as a V-shaped grading blade or a spinning tube finisher could be used as a substitute for the disclosed rotating auger distributing means. Accordingly, it is intended by the appended claims to cover all such modifications of the invention which fall within the true spirit and scope of the invention.