Patent Grant
8517630
The present disclosure relates to asphalt paving machines, and, more particularly, to a screed arrangement and a method of attaching a screed plate to a screed assembly.
Laying asphalt paving material on road surfaces entails spreading paving material consisting of an aggregate filled bituminous mixture on a prepared roadbed. The paving material is spread while hot and is then compacted so that a hardened pavement surface is formed upon cooling. Conventional paving machines utilize a heavy assembly termed a “screed” that is drawn behind the paving machine. The screed assembly includes a replaceable screed plate that is constructed of a suitable steel, to spread a smooth even layer of paving material on the prepared roadbed. The weight of the screed assembly aids in compressing the paving material and performing initial compaction of the paving material layer. Screed assemblies can include vibratory mechanisms placed directly on the screed plate or separate vibratory tamper bars connected in tandem with the screed plate to aid in the initial compaction of the paving material.
To facilitate laying of the paving material, the screed plate is typically heated, to a temperature in the range of about 82° to 171° C. (180° to 340° F.). Heating the screed plate assists the paving material in flowing under the screed plate and reduces adhesion of the paving material to the screed plate. If the screed plate is not adequately heated, the bituminous mixture contacting the bottom of the screed plate begins to harden, resulting in buildup of paving material and excessive drag.
Conventional screed plates are commonly heated by fossil fuel powered burners that heat the upper surface of the screed plate by the direct application of flame or hot exhaust gases. The use of fossil fuel burners to heat screed plates has several drawbacks. Combustion of fossil fuels generates smoke that represents a source of environmental pollution, and also poses a poor working environment for the paving workers. Additionally, because the flames or exhaust gases of the burners actually contact the screed surface, warping may result. The contour of the screed plate determines the quality, evenness and smoothness of the paving material that is being laid down. Screed plates are often flexed under extreme tensile loads during use to achieve desired crowning or other surface contours.
One alternate heating system that represents an improvement and which addresses the environmental drawbacks is disclosed in U.S. Pat. RE 36,981 issued Dec. 5, 2000 to Ralph Birtchet and assigned to Universal Screed Inc. Birtchet discloses the use of an elastomeric, electrically powered heating pad assembly positioned on the upper surface of the screed plate with a layer of insulation placed on top of the heating pad assembly. A heavy steel retainer plate assembly is disposed on top of the insulation to hold the heating pad assembly and the insulation in contact with the screed plate. But for the retainer plate assembly, the heating pad assembly and the layer of insulation are loosely positioned on the upper surface of the screed plate, mechanically constrained in their installed positions only by the forward face plate portion and the tail portion of the screed plate, and the side plates. The screed plate is attached directly to the deck plate of the paving machine.
Assembling the screed plate to the paving machine is generally a time consuming process because the screed plate must be precisely oriented relative to the frame. Assembly of the screed plate to the frame typically involves time consuming shimming operations. Inasmuch as the screed plate is a wear component, replacement due to wear may result in considerable downtime, often for days inasmuch as this shimming process must be repeated. Similar delays may result when the screed plate is removed to access the heating assembly for replacement or repair.
The disclosure describes, in one aspect, an asphalt paving machine comprising a screed assembly, a screed plate assembly, at least two lower plate fasteners, and at least two upper plate fasteners. The screed assembly includes a screed supporting frame portion having at least two first bores and at least two second bores. The screed plate assembly includes at least one lower screed plate having at least two openings, at least one upper screed plate having at least two openings, and at least one electric heater at least partially disposed between the upper and lower screed plates. The lower plate fasteners extend into the at least two openings of the lower screed plate and the at least two first bores of the screed supporting frame portion to couple the lower screed plate to the screed supporting frame portion. The upper plate fasteners extend into the at least two openings of the upper screed plate and the at least two second bores of the screed supporting frame portion to couple the upper screed plate to the screed supporting frame portion independently of the lower screed plat. The lower plate is displaceable from the upper screed plate and the screed supporting frame portion by loosening the at least two lower plate fasteners.
The disclosure also describes, in one aspect, a screed plate assembly for attachment to a screed supporting frame portion of an asphalt paving machine. The screed supporting frame portion has at least two first bores and at least two second bores. The screed plate assembly includes at least one lower screed plate having at least two openings, at least one upper screed plate having at least two openings, at least one electric heater at least partially disposed between the upper and lower screed plates, at least two lower plate fasteners adapted to extend into the at least two openings of the lower screed plate and the at least two first bores of the screed supporting frame portion to couple the lower screed plate to the screed supporting frame portion, and at least two upper plate fasteners adapted to extend into the at least two openings of the upper screed plate and the at least two second bores of the screed supporting frame portion to couple the upper screed plate to the screed supporting frame portion independently of the lower screed plate. The lower plate is displaceable from the upper screed plate and the screed supporting frame portion by loosening the at least two lower plate fasteners.
The disclosure describes in another aspect a method of attaching a screed plate assembly to a screed assembly of an asphalt paving machine, wherein the screed assembly includes a screed supporting frame portion. The method includes providing at least two first bores and at least two second bores in the screed supporting frame portion, providing a screed plate assembly including at least one lower screed plate having at least two openings, at least one upper screed plate having at least two openings, and at least one electric heater disposed between the upper and lower screed plates, extending at least two upper plate fasteners into the at least two openings of the upper screed plate and the at least two second bores of the screed supporting frame portion to secure the upper screed plate to the screed supporting frame portion, and extending at least two lower plate fasteners into the at least two openings of the lower screed plate and the at least two first bores of the screed supporting frame portion to secure the lower screed plate to the screed supporting frame portion, the at least two upper plate fasteners securing the upper screed plate to the screed supporting frame portion independently of the lower screed plate.
This disclosure relates to a design and mounting arrangement for coupling a screed plate to a screed assembly 12 of an asphalt paving machine 10, as shown in
The screed assembly 12 is pivotally connected behind the asphalt paving machine 10 by tow arms 18. The screed assembly 12 may be any of a number of configurations such as a fixed width screed or a multiple section screed that includes extensions. As shown in
Turning to
The screed plate assembly 30 includes an upper screed plate 36 and a lower screed plate 38, both of which are coupled to the screed supporting frame portion 32. The lower screed plate 38 is an elongated largely flat metal plate having an upper surface 40 and a lower surface 42 positioned between a leading edge 44 and the trailing edge 46. In the illustrated embodiment, the upper screed plate 36 is likewise a largely flat structure, although it may be of an alternate configuration so long as the upper and lower screed plates 36, 38 are coupled to the screed supporting frame portion 32 as described herein.
According to a feature of the disclosed screed plate assembly 30, the upper screed plate 36 is coupled to the screed supporting frame portion 32 independently of the lower screed plate 38. In this way, as illustrated in
The upper screed plate 36 is coupled to the screed supporting frame portion 32 by at least two connectors 50, 52, and the lower screed plate 38 is coupled to the screed supporting frame portion 32 by at least two connectors 54, 56. While any appropriate connecting arrangement may be utilized, in the illustrated embodiment, the screed supporting frame portion 32 includes a plurality of bores 60, 62, 64, 66 through which connectors 50, 52, 54, 56 from the upper and lower screed plates 36, 38 extend. More specifically, connectors 50, 52 extend from the upper screed plate 36 through first bores 60, 62 in the screed supporting frame portion 32, and connectors 54, 56 from the lower screed plate 38 extend through the second bores 64, 66 of the screed supporting frame portion 32.
The connectors 50, 52, 54, 56 may be of any appropriate design. By way of example only, the connectors 50, 52, 54, 56 may be threaded fasteners, as illustrated, which are received by locking nuts 68. It will be appreciated that the connectors 50, 52, 54, 56 may extend through openings 70, 72 in the upper and lower screed plates 36, 38, or they may be otherwise secured to the upper and lower screed plates 36, 38. For example, they may be secured in openings 70, 72 in the form of recesses in the upper and lower screed plates 36, 38. In this way, the term “openings” is intended to include both bores that extend completely through the upper and lower screed plates 36, 38, as well as recesses that extend only partway through the thickness of the upper and lower screed plates 36, 38.
The upper screed plate 36 may include openings 74 that allow for passage of the connectors 54, 56 extending from the lower screed plate 38 toward the screed supporting frame portion 32. The openings 74 may be of any appropriate design. For example, the openings 74 may be generally round or they may be slots (not shown) that extend from the sides surfaces 76 of the upper screed plate 36 to accommodate passage of the connectors 54, 56.
Each screed plate assembly 30 is heated by a screed heating arrangement 80. The screed heating arrangement 80 includes at least one electric heater 82 positioned to heat at least the lower screed plate 38. A greater number electric heaters 82 may be provided for each screed plate assembly 30, as shown, for example, in
Each electric heater 82 is connected to an electric power supply 88, shown in
Any appropriate design of electric heater 82 may be utilized. The electric heater 82 in the illustrated embodiment is configured as a thin, elongate sheet or ribbon and formed from a resistive conductor, e.g., a thin conductive wire or ribbon. It will be appreciated, however, that alternate designs of electric heaters 82 may be utilized, such as, electric heaters 82 that present a broader profile. A resistive conductor within each electric heater 82 terminates with a set of leads 86 or electrical conductors that protrude from the electric heater 82.
In the illustrated embodiment, the electric heater 82 is sandwiched between the upper and lower screed plates 36, 38. Consequently, displacing the lower screed plate 38 from the upper screed plate 36 and the screed supporting frame portion 32, as shown in
The upper and lower screed plates 36, 38 may be made of any appropriate material. By way of example only, the lower screed plate 38 may be constructed of a high wear steel, while the upper screed plate 36 may be formed of steel, a ferrous material, or composite insulating material. For example, the upper screed plate 36 may be formed of a material which assists in conducting heat from the electric heater 82 to the lower screed plate 38 to enhance heating of the lower screed plate 38. Alternatively or additionally, the upper screed plate 36 may be formed of a material that provides an insulative effect, which may minimize heat loss from the electric heater 82 and the lower screed plate 38.
Returning to
The present disclosure is applicable to screed plate assemblies 30 and their attachment to asphalt paving machines 10. The screed plate assembly 30 including upper and lower screed plates 36, 38 may reduce the time associated with repair or replacement of the lower screed plate 38 or the electric heater 82. In some embodiments, when the lower screed plate 38 is displaced from the upper screed plate 36 and the screed supporting frame portion 32, the electric heater 82 may be simply slid out from between the upper and lower screed plates 36, 38. A replacement electric heater 82 may then be slid back into position before the lower screed plate 38 is again moved toward the upper screed plate 36 and the screed supporting frame portion 32.
Maintaining the mounted upper screed plate 36 in position while displacing the lower screed plate 38 from the upper screed plate 36 and the screed supporting frame portion 32 may reduce or eliminate entirely the time associated with calibrating attachment of the screed plate assembly 30 to the screed supporting frame portion 32, that is, the screed plate assembly 30 generally will not require the complete shimming process typically associated with mounting of a screed plate assembly 30.
Placement of the electric heater 82 between the upper and lower screed plates 36, 38 may enhance efficiency of the heating arrangement 80. Heating of the lower screed plate 38 may be improved by way of enhanced conduction of heat from the electric heater 82 to the lower screed plate 38, or by enhancing the consistency of heat transmitted to the lower surface 42 of the lower screed plate 38.
In some embodiments, placement of the electric heater 82 between the upper and lower screed plates 36, 38 may leave the upper surface of the upper screed plate 36 for placement of additional insulating blankets, or mounting a vibration pod directly to the screed plate assembly 30.
During operation of the asphalt paving machine 10, the electric heater 82 flexes with the screed plate assembly 30 as the paving machine 10 traverses the road bed were asphalt paving material is being laid. When a thin design of the electric heater 82 is utilized, the placement of the electric heater 82 between the upper and lower screed plates 36, 38 may act to minimize stresses on the electric heater 82.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3872601 | Burgin | Mar 1975 | A |
| 5088854 | Sovik | Feb 1992 | A |
| 5259693 | Raymond | Nov 1993 | A |
| 5308190 | Raymond | May 1994 | A |
| 5366320 | Hanlon et al. | Nov 1994 | A |
| 5397199 | Frampton et al. | Mar 1995 | A |
| RE36981 | Birtchet | Dec 2000 | E |
| 6273636 | Johanpeter | Aug 2001 | B1 |
| 6318928 | Swearingen | Nov 2001 | B1 |
| 6963050 | Heindtel | Nov 2005 | B2 |
| 6981820 | Nelson | Jan 2006 | B2 |
| 8157474 | Mahler et al. | Apr 2012 | B2 |
| 20010014212 | Rutherford | Aug 2001 | A1 |
| 20040086336 | Nelson | May 2004 | A1 |
| 20060045624 | Nelson | Mar 2006 | A1 |
| 20100310312 | Mahler et al. | Dec 2010 | A1 |
| 20110002737 | Mahler et al. | Jan 2011 | A1 |
| 20110002738 | Mahler et al. | Jan 2011 | A1 |
| 20110123269 | Lutz | May 2011 | A1 |
| Number | Date | Country |
|---|---|---|
| 641887 | Jul 1997 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20130142571 A1 | Jun 2013 | US |
