US20020061227A1

US20020061227A1 - Metering and leveling screed device

Info

Publication number: US20020061227A1
Application number: US09/797,133
Authority: US
Inventors: Christopher Rahn; Brian Hawkins
Original assignee: Blaw Knox Construction Equipment Co
Current assignee: Blaw Knox Construction Equipment Co
Priority date: 2000-03-03
Filing date: 2001-03-01
Publication date: 2002-05-23

Abstract

The present invention is directed to a screed assembly that includes a strike-off. This strike-off is directly connected to a screed plate such that the strike-off is able to bend or twist along with movement of the screed plate which occurs during a paving operation. The strike-off in the screed assembly of the present invention is simpler and less costly to manufacture than corresponding devices in existing screed assemblies. Connecting the strike-off directly to the screed establishes a shearing height prior to mounting the screed assembly to the paving machine in set up of the screed assembly faster and easier to accomplish.

Description

This application claims priority to provisional application Ser. No. 60/186,779, filed Mar. 3, 2000, the entire contents of which are incorporated herein by reference.[0001]

FIELD OF THE INVENTION

The present invention relates to paving vehicles, and more particularly to screed assemblies used with paving vehicles.

BACKGROUND OF THE INVENTION

Paving vehicles or pavers having floating screed assemblies are known, an example of one such screed

assembly

1 being shown in FIG. 1. Generally, a conventional screed assembly 1 is pivotally attached to a paver vehicle chassis (not shown) and has a screed plate 2 mounted beneath a frame 3. The screed plate 2 has a lower surface 2 a which levels paving material into a material mat (not depicted) having a desired height or thickness as the paver vehicle moves forwardly in a paving direction.

Typically, these

screed assemblies

1 also include a strike-off device 4 adjustably attached to the screed frame 3 which shears off paving material to an initial height prior to being leveled by the screed plate 2. Strike-off devices 4 typically include a vertically-extending plate 5 providing a strike-off edge 4 a at the lower end thereof and an adjustment mechanism 6 for adjusting the height h_oof the edge 4 a with respect to the working surface 2 a. For example, the adjustment mechanism 6 may include one or more rods 7 having an end 7 a attached to the strike-off plate 5 and a portion 7 b movably mounted to the frame 3, such that movement of the rod 7 with respect to the frame 3 adjusts the height h_o.

With such

screed assemblies

1, as discussed above, it is necessary to adjust the strike-off edge 4 a to the desired height h_owith respect to the screed working surface 2 a prior to commencing a paving operation. Thus, such adjustment of the strike-off device 4 increases the set-up time of the screed assembly 1. As screed plates 2 become worn and must be periodically replaced, the strike-off device 4 is typically adjusted numerous times over the life of the screed assembly 1. Further, as paving material generally causes a certain amount of bending and/or twisting of the screed plate 2 during a paving operation, the height h_obetween the strike-off edge 4 a and the working surface 2 a will become varied across the width of the screed assembly 1. These unintended variations of the strike-off height h_oeffect the amounts of paving material metered to the screed plate 2, such that sections/portions of a finished material mat may be formed at other than a desired thickness.

SUMMARY OF THE INVENTION

Therefore, it is desirable to provide a screed

assembly

1 that is quicker and easier to set-up before use. Further, it is also desirable to provide a strike-off device that is simpler and requires less material to manufacture than known strike-off devices. Furthermore, it is desirable to prevent variations in the height or spacing of a strike-off edge with respect to a screed working surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the detailed description of the preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, which are diagrammatic, embodiments that are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: [0007]
FIG. 1 is a side elevational view of a screed assembly with a known type of strike-off device; [0008]
FIG. 2 is a side elevational view of a screed assembly having a metering and leveling screed device in accordance with the present invention; [0009]
FIG. 3 is a top perspective view of the present screed device; and [0010]
FIG. 4 is an exploded side view of the present screed device.[0011]

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “lower”, “upper”, and “upward” designate directions in the drawings to which reference is made. The words “front” and “rear” refer to directions toward and away from, respectively, a designated front section of a screed assembly, a metering and leveling screed device or a specific portion of either, the particular meaning intended being readily apparent from the context of the description. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import. [0012]
Referring now to the drawings in detail, wherein like numbers are used to indicate like elements throughout, there is shown in FIGS. [0013] 2-4 a metering and leveling screed device 10 comprising a leveling portion, preferably a screed plate 12, and a metering portion, preferably a strike-off 14 connected to the screed plate 12. Preferably, the strike-off 14 is fixedly attached to the screed plate 12, as depicted in FIGS. 2 and 3, although the strike-off 14 may alternatively be adjustably attached to, or even integrally formed with, the screed plate 12, as discussed in further detail below. The strike-off 14 portion of the device 10 shears upper portions of a deposit or “head” of paving material in order to meter appropriate amounts of paving material to the screed plate 12 portion of the device 10 for subsequent leveling and compacting, as discussed in further detail below.
The [0014] screed plate 12 is preferably formed similar to a conventional screed plate 2. Specifically, the plate 12 is primarily of one piece-construction and includes a generally horizontal base section 16 and a generally vertical rail section 18 extending upwardly along the front end of the base section 16. The lower surface of the base section 16 provides the working or leveling surface 15 of the screed assembly and functions to level paving material deposited on a base surface, as is well known. Further, a plurality of mounting studs 25 extend from the upper surface of the base section 16 and are configured for mounting the screed plate 12, and thus the device 10, to the screed assembly 1 in a conventional manner.
The [0015] rail section 18 has a front surface 20 that includes a lower, curved lead-in or channeling surface section 20 a that functions to channel paving material to the working surface 15. Further, the rail section front surface 20 also includes an upper, generally flat attachment surface section 20 b configured to connect with the strike-off 14. The rail section 18 further includes a plurality of mounting holes 21 (FIG. 4—one shown) spaced horizontally across the attachment surface section 20 b, the purpose of which is described below. Besides providing the respective lead-in and attachment surface sections 20 a and 20 b and the mounting holes 21, the rail section 18 also operates as a barrier to prevent paving material from flowing onto, and accumulating upon, the upper surface of the screed plate 12.
Preferably, the [0016] screed plate 12 is fabricated by bending one edge of generally flat plate in a (lie-forming operation so as to form the rail section 18 and then welding the studs 25 onto the upper surface of the base section 16. Further, the screed plate 12 is preferably constructed of high carbon steel, most preferably either WELDOX™ or HARDOX™ commercially available grades of steels. Alternatively, the screed plate 12 may be formed using any other appropriate manufacturing technique, such as for example casting, and/or may be constructed on another appropriate material, for example low carbon steel that has been appropriately hardened such as by carburization.
Referring again to FIGS. [0017] 2-4, preferably, the strike-off 14 includes one or more (two shown) generally flat and narrow, rectangular-shaped plates or “blades” 22 having a generally uniform thickness. The lower end of each strike-off blade 22 provides the working or “strike-off” edge 24, as discussed below. Each blade 22 has a generally flat rear surface 22 a that is configured to be disposed against the attachment surface section 20 b of the screed plate 12, as discussed below. Further, a plurality of horizontally-spaced mounting holes 26 (FIG. 4—one shown) extend through each blade 22, which are configured to align with the mounting holes 21 in the rail section 18 of the screed plate 12, as discussed below. Preferably, the strike-off blades 22 are stamped from low carbon steel, although the strike-off 14 may alternatively be fabricated using any other appropriate material and/or manufacturing technique, such as for example, being machined from tool steel (although not preferred due to costs).
Although the strike-[0018] off 14 is preferably constructed as two generally flat blades 22 as described above, the strike-off 14 may alternatively be formed in any other appropriate configuration that is capable of being attached to the screed plate 12. For example, the strike-off 14 may include only a single blade or three or more blades/blade sections (neither shown). Further, the blades 22 may each have varying thickness, such as being tapered or stepped, between the upper and lower ends of the blade 22, as opposed to being of uniform thickness. Further for example, the strike-off 14 may be constructed as bended or angled plate (not shown) having a lower end extending forwardly from an upper end, so that the strike-off edge 24 is spaced substantially forwardly of the screed plate 12, particularly if it is desired that the strike-off 14 perform a material “plowing” function as well as shearing.
As yet another example, the [0019] edges 24 of the two blades 22 may each be angled so as to extend upwardly from a blade outer end (i.e., outer with respect to center of device 10) to a blade inner end (not shown), or a single blade may have an equivalent triangular-shaped edge (not shown), such that a greater amount of material is metered under the central region of the screed plate 12. As an even further example, the strike-off 14 may be constructed of two or more pieces, such as one or more brackets attachable to the screed plate 12 and a blade(s) mountable to the brackets (not shown). The present invention includes the above alternative constructions of the strike-off 14 and any other appropriate configuration that enables the strike-off 14 to be directly attached to the screed plate 12.
Referring again to FIGS. 2 and 3, the strike-[0020] off 14 is mounted to the screed plate 12 by placing the rear blade surfaces 22 a against the attachment surface section 20 b of the rail 18 such that the several pairs of mounting holes 21 and 26 are aligned, and then inserting threaded fasteners 27 through the mounting hole pairs 21 and 26. In the preferred construction as described, the strike-off 14 is fixedly or non-adjustably attached to the screed plate 12. Therefore, when the strike-off 14 is attached as described, the strike-off edge 24 is automatically established at a desired height h_d(FIG. 2) with respect to the leveling surface 15.
Alternatively, the strike-[0021] off 14 may be non-removably attached to the screed plate 12, such as by forming a riveted or welded joint between the strike-off blade 22 and the rail section 18. As another alternative, the strike-off 14 may be integrally formed with the screed plate 12, such as by die-forming or casting the entire screed device 10 so as to be of one-piece construction.
As an even further alternative, the strike-[0022] off 14 may be adjustably (and removably) attached to the screed plate 12, such as by providing slotted openings in place of one (or both) sets of mounting holes 21 and 26. With an adjustably attached strike-off plate 14 (configuration not depicted), the strike-off edge 24 should be adjusted to the desired height h_dprior to attaching the device 10 to the frame 3, although such adjustment may alternatively be performed after mounting of the device 10.
Prior to use, as mentioned above, the metering and leveling screed device [0023] 10 is attached to the frame 3 of a screed assembly 1 in a generally identical manner as a conventional screed plate 2. Specifically, the mounting studs 25 are each inserted through a mating opening (not shown) in the screed frame 3 and are engaged by nuts (not show) to removably mount the screed device 10 to the frame 3. As the strike-off edge 24 is preferably at a specific, desired height h_dwith respect to the leveling surface 15, no further adjustment of the screed device 10 should be necessary.
Although the metering and leveling screed device [0024] 10 of the present invention is depicted in FIG. 2 as being mounted to a single “main” screed assembly 1, it is within the scope of the p-resent invention to use the present screed device 10 with any type of screed assembly 1 that is configured to include one or more screed plates. For example, the screed device 10 may be mounted to a single main screed configured for a single screed plate, to a main screed formed of two screed halves (thus having two screed plates) so as to provide crowning, to a fixed screed extension, and/or to a laterally movable or “extendable” screed extension. Thus for example, a screed assembly 1 including a main screed formed of two “crownable” screed halves and two extendable screed extensions (not shown) may include four screed devices 10 of the present invention. Thus, the present invention is not limited to being used with any specific type of screed assembly 1.
In use, as the [0025] screed assembly 1 is pulled forwardly by the paver vehicle (not shown), the strike-off edge 24 “shears off” upper portions of a mass of paving material deposited forwardly of the assembly 1 by the paver vehicle, and thereby establishes a first material height or material level of the material. Then, paving material is channeled by action of the channeling surface section 20 a of the screed plate 12 so as to flow beneath the leveling surface 15. The screed leveling surface 15 then levels and preferably also compacts the paving material into a material mat (not shown) having a desired thickness or height (not shown).
Providing a [0026] screed assembly 1 with the metering and leveling screed device 10 of the present invention is clearly advantageous over prior screed assemblies 1 having a separate screed plate 2 and a separate strike-off device 4. First, by having the strike-off 14 directly connected to the screed plate 12, the strike-off 14 is able to bend or twist along with such movement of the screed plate 12 occurring during a paving operation, such that the desired strike-off height h_dis generally always maintained. Further, the strike-off 14 portion of the present device 10 is much simpler and less costly to produce than a strike-off device 4 having a large plate 5 and an adjustment mechanism 6 including one or more movable rods 7. Furthermore, by being able to establish the desired height h_dprior to mounting the device 10 to the screed assembly 1, either automatically when attaching the blade(s) 22 to the rail 18 or by adjusting the blade(s) before mounting the device 10, the set-up of a screed assembly 1 with the device 10 is faster and easier to accomplish than separately adjusting the vertical strike-off plate 5 with respect to a separate screed plate 2.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as generally and illustratively described herein. [0027]

Claims

1. A screed assembly for use with a paving machine, the screed assembly comprising:

a screed including a front portion, a rear portion and a rounded portion positioned between the front portion and the rear portion; and

a strike-off coupled to the screed.

2. The screed assembly of claim 1 wherein the strike-off is coupled to the front portion of the screed.

3. The screed assembly of claim 2 wherein the front portion of the screed includes a front surface such that the strike-off is coupled to the front surface on the front portion of the screed.

4. The screed assembly of claim 3 wherein the strike-off includes a rear surface such that the rear surface of the strike-off is coupled to the front surface on the front portion of the screed.

5. The screed assembly of claim 4 wherein the rear surface of the strike-off and the front surface of the front portion are substantially flat.

6. The screed assembly of claim 1 wherein the strike-off is integral with the screed.

7. The screed assembly of claim 1 wherein the screed plate has a one-piece construction.

8. The screed assembly of claim 1 wherein the rear portion of the screed includes a lower leveling surface for compacting paving material.

9. The screed assembly of claim 8 wherein the rear portion of the screed includes at least one stud extending outwardly from an upper surface on the rear portion, the screed assembly being secured to a frame on the paving machine by securing the stud to the frame of the paving machine.

10. The screed assembly of claim 1 wherein the strike-off and the screed each include aligned mounting holes, and the strike-off is connected to the screed using fasteners that extend through the aligned mounting holes.

11. The screed assembly of claim 1 wherein the strike-off is welded to the screed.

12. The screed assembly of claim 1 wherein the strike-off is made from low carbon steel.

13. The screed assembly of claim 1 wherein the screed is made from high carbon steel.

14. The screed assembly of claim 1 wherein the strike-off includes at least one blade.

15. The screed assembly of claim 14 wherein the strike-off includes two blades.

16. The screed assembly of claim 15 wherein each of the blades is rectangular.

17. The screed assembly of claim 15 wherein each of the blades has a substantially uniform thickness.

18. The screed assembly of claim 15 wherein each of the blades is formed from angled plate material.

19. The screed assembly of claim 1 wherein the strike-off is riveted to the screed.

20. The screed assembly of claim 1 wherein the strike-off includes slotted openings and the screed includes mounting holes which are aligned with the slotted openings on the strike-off such that strike-off is adjustably mounted to the screed using fasteners that extend through the mounting holes and the slotted openings.

21. The screed assembly of claim 1 wherein the screed includes slotted openings and the strike-off includes mounting holes which are aligned with the slotted openings on the screed such that strike-off is adjustably mounted to the screed using fasteners that extend through the mounting holes and the slotted openings.

22. A screed assembly for leveling and compacting paving material within a paving machine, the screed assembly comprising:

a strike-off for shearing upper portions of a mass of paving material that is deposited forwardly of the screed assembly by the paving machine; and

a screed coupled to the strike-off, the screed including a front portion, a rear portion and a rounded portion positioned between the front portion and the rear portion such that the front portion of the screed prevents the paving material from flowing over on top of the screed and is instead channeled by the rounded portion to flow beneath a leveling surface on the rear portion in order to level and compact the paving material.

23. A screed assembly for use with a paving machine, the screed assembly comprising:

a one-piece screed including a front portion, a rear portion and a rounded portion positioned between the front portion and the rear portion, the front portion of the screed including a front surface and the rear portion of the screed including a lower leveling surface for compacting paving material; and

a strike-off including at least one blade such that each of the blades includes a rear surface which is coupled to the front surface on the front portion of the screed.

24. The screed assembly of claim 1 wherein the strike-off and screed each include aligned mounting holes and the strike-off is connected to the screed using fasteners that extend through the aligned mounting holes.