The present disclosure generally relates to screed assemblies for paving machines, and more specifically, to systems and methods for preventing paving material leakage between main screeds and extension screeds when the extension screeds are fully-extended.
Paving machines are used to lay and level a paving material, such as asphalt, on a ground surface for the construction of roads, bridges, parking lots, and other such surfaces. In general, paving machines include a chassis, a hopper for storing the paving material, an auger that distributes the paving material on a ground surface, and a screed assembly that compacts/levels the paving material to a desired mat thickness. The screed assembly may be rear-mounted on the paving machine behind the hopper, the chassis, and the auger relative to the direction of travel. The screed assembly may include a main screed and one or more extension screeds mounted behind (or in front of) the main screed. The extension screeds are laterally extendable from the main screed to adjust for varying ground surface widths. In addition, the main screed and the extension screeds may each include a bottom-facing screed plate that compacts the paving material on the ground surface at a pre-determined “angle of attack”. Some screed assembly designs may also include a tamper bar at the front of the main and/or extension screeds that move up and down vertically to pre-compact the paving material in front of the main and/or extension screeds.
While effective, uncompacted paving material may be prone to leak through a gap between the main screed and the extension screeds, when the extension screeds are fully-extended. This may ultimately lead to undesirable streaks of uncompacted paving material that trail behind the paving machine. This problem may be more prevalent with screed assembly designs having tamper bars because the tamper bars may push the paving material forward, causing it to bypass other systems designed to block paving material leakage between the main and extension screeds.
U.S. Pat. No. 6,106,192 addresses the problem of mat streaking in paving machines caused by overlapping edges of front-mounted extendible screeds a rear-mounted central main screed. In this case, the streaks are formed from compacted material that is more densely compressed and shinier than the rest of the mat. To prevent the formation of the shiny streaks, a flow-modifying device is disclosed that plows the paving material at the outer edges of the main screed toward the central axis of the main screed. However, the flow-modifying device disclosed therein does not address or correct the problem of streaks of uncompacted material caused by paving material leakage through gaps between the main and extension screeds. Moreover, the flow-modifying device is specifically designed for paving machines having front-mounted (not rear-mounted) extendible screeds.
There is a need for screed assembly designs that prevent the leakage of paving material between the main screed and rear-mounted extension screeds when the extension screeds are fully-extended.
In accordance with one aspect of the present disclosure, a screed assembly for a paving machine is disclosed. The screed assembly may comprise a main screed and an extension screed configured to extend from the main screed to a fully-extended position. The extension screed and the main screed may define a gap therebetween when the extension screed is in the fully-extended position. The extension screed may include a deflector and a material bypass prevention plate affixed to the extension screed. The material bypass prevention plate may have a projection that extends into and fills a space between the material bypass prevention plate and the main screed when the extension screed is in the fully-extended.
In accordance with another aspect of the present disclosure, a paving machine is disclosed. The paving machine may be configured to pave a paving material on a ground surface and may comprise a chassis, a hopper configured to carry the paving material, and a distributing device configured to distribute the paving material on the ground surface. The paving machine may further comprise a screed assembly that may include a main screed and an extension screed configured to extend from the main screed to a fully-extended position. The extension screed may include a deflector and a material bypass prevention plate affixed to the extension screed. The material bypass prevention plate may have a projection that extends into and fills a space between the material bypass prevention plate and the main screed when the extension screed is in the fully-extended position.
In accordance with another aspect of the present disclosure, a method for preventing a paving material from leaking through a gap between a main screed and an extension screed of a screed assembly when the extension screed is in a fully-extended position is disclosed. The extension screed may be axially aft of the main screed and may have a tamper bar. The method may comprise attaching a material bypass prevention plate to the extension screed such that a projection of the material bypass prevention plate extends into and fills a space between the material bypass prevention plate and the main screed, and such that a chamfer on an aft-facing edge of the projection is axially forward of and contours the tamper bar. The method may further comprise allowing a portion of the paving material to flow to toward the gap and between the tamper bar and the aft-facing edge, and using the chamfer to prevent compaction of the portion of the paving material between the tamper bar and the aft-facing edge. The method may further comprise redirecting the portion of the paving material between the tamper bar and the aft-facing edge to a front of the extension screed with the chamfer, and paving the portion of the paving material with the extension screed.
These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings.
Referring now to the drawings, and with specific reference to
Turning now to
The main screed 32 includes a generally vertically-extending deflector 38, and may also include a tamper bar 40 disposed near a bottom edge of the deflector 38 that moves up and down vertically to pre-compact the paving material 12 in front of the main screed 32. In addition, the main screed 32 has side plates 42 mounted on the laterally outward-facing sides of the main screed 32 and oriented perpendicular to the deflector 38, as well as a generally downward-facing (i.e., towards the ground surface 14) and horizontally-extending main screed plate 44 that may contact and compact the paving material 12 at a set “angle of attack” (i.e., the angle that the screed plate 44 makes with the ground surface 14) as will be understood by those with ordinary skill in the art of paving machines (see
Likewise, each of the extension screeds 34 include a generally vertically-extending deflector 46, and may also include a tamper bar 48 along a bottom edge of the deflector 46 that may move up and down to pre-compact the paving material 12 in front of the extension screed 34. In addition, each of the extension screeds 34 include a generally downward-facing and horizontally-extending extension screed plate 50 that contacts and compacts the paving material 12 at a set angle of attack (see
Referring now to
In addition, the material bypass prevention plate 68 includes a projection 72 extending from a laterally outward-facing surface 74 of the plate 68 (see
In one aspect of the present disclosure, the projection 72 is a second plate 78 affixed to the forward end 76 of the laterally outward-facing surface 74 of the plate 68 (also see
In contrast, in the absence of a chamfer at the first surface 84 and the second surface 88 (i.e., with the surfaces 84 and 88 oriented parallel to the surfaces 86 and 90 of the tamper bar), paving material could become compacted between the tamper bar 48 and the surfaces 84 and 88, potentially causing sticking or dragging of clumps of compacted material that could leave marks or other inhomogeneities in the mat 16. Thus, the chamfers 92 prevent the compaction of paving material between the tamper bar 48 and the aft-facing edge 80 of the projection 72, and are configured to channel any paving material that flows between the tamper bar 48 and the aft-facing edge 80 to the front of the extension screed 34 for paving.
The material bypass prevention plate 68 is affixed to the extension screed 34 using fasteners, such as bolts 94 (see
Turning now to
The plate 68 also includes a laterally inward-facing surface 108 through which bolts 94 are inserted if the plate is affixed to the extension screed with fasteners (see
A series of steps involved in using the material bypass prevention plate 68 to prevent the leakage of the paving material 12 between the main screed 32 and the extension screed 34 when the extension screed 34 is in the fully-extended position 37 is shown in
As the paving machine 10 travels in the forward direction, a portion of the paving material 12 is permitted to flow between the tamper bar 48 and the aft-facing edge 80 of the projection 72 according to a next block 124. The chamfers 92 on the aft-facing edge 80 are then used to prevent compaction of the paving material 12 between the tamper bar 48 and the aft-facing edge 80 of the projection 72 as explained above (block 126). Further, the chamfers 92 may advantageously redirect the paving material between the tamper bar 48 and the projection 72 toward the front of the extension screed 34 (block 128). Once redirected to the front of the extension screed 34, the paving material 12 is pre-compacted with the tamper bar 48 and paved under the extension screed plate 50 according to a next block 130.
The teachings of the present disclosure are beneficial to paving machines, and more particularly to paving machines having extension screeds. The material bypass prevention plate disclosed herein is affixed to an extension screed of a screed assembly to prevent uncompacted paving material from leaking between the extension screed and the main screed when the extension screed is in the fully-extended position. In addition, the material bypass prevention plate has a laterally-outward extending projection that extends into and fills a space between the material bypass prevention plate and the main screed side plate to further prevent the paving material from being pushed forward and around the material bypass prevention plate by the up and down movement of the tamper bar. The aft-facing edge of the projection contours the laterally inward edge of the tamper bar, and is provided with one or more chamfers. The chamfers are configured to prevent compaction of paving material between the tamper bar and the aft-facing edge, as well as redirect the uncompacted paving material to the front of the extension screed where it may be uniformly paved under the extension screed plate with the bulk of the paving material. Thus, the material bypass prevention plate disclosed herein supports paving uniformity in paving machines with extension screeds fully-extended by blocking uncompacted paving material leakage between the main screed and the extension screed, by preventing the paving material from bypassing the plate by the forward-pushing movement of the tamper bar, by preventing compaction of paving material between the tamper bar and the aft-facing edge of the projection which could otherwise lead to inhomogenous marks on the mat, and by channeling the paving material between the tamper bar and the projection to the front of the extension screed. It is also noted that the teachings of the present disclosure may also be applicable to paving machines having extension screeds that are bolted onto the screed assembly to provide greater paving widths.
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20160265173 A1 | Sep 2016 | US |