Abstract:
In a slip-form paving apparatus, a forwardly disposed pavement forming assembly, such as an auger assembly and a strike-off plate, are pivotably mounted to the apparatus frame for movement between an operative disposition disposed adjacent a ground surface for distributing and forming paving material thereon generally into a desired form of pavement and an inoperative position more elevated from the ground surface for permitting access beneath the apparatus for depositing a starting quantity of the paving material during an initial start-up of the apparatus.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to apparatus for forming concrete or other flowable paving material into a paved surface and, more particularly, to such a paving apparatus of the self propelled type for continuous slip-form paving of roadways, sidewalks and like concrete pavement surfaces. 
     Self-propelled construction vehicles and other construction equipment of diverse types are well known. One type of such construction equipment are so-called slip-form paving machines essentially adapted to continuously form concrete or another flowable paving material along the ground or other base surface, for example, to form a roadway. Diverse forms of such machines have been described in prior patents, representative examples of which may be found in U.S. Pat. Nos. 3,175,478; 3,264,958; 3,637,026; 3,771,892; 3,970,405; 4,197,032; 4,360,293; 4,925,340; 4,948,292; 5,044,820 and 5,590,977. 
     Conventionally, it is commonplace for paving equipment of this type to support the machine frame on a plurality of drivable transport assemblies, such as so-called crawler track assemblies, adapted to facilitate steerable driving of the paving machine over substantially any ground surface along which a roadway or like surface is to be paved. The frame of the machine is equipped with various devices and mechanisms to perform various functions of the paving operation, including typically an auger or other suitable mechanism for distributing the paving material laterally across the front of the machine, followed by a vertically disposed plate or like structural member, commonly referred to as a strike-off plate, positioned with a lower edge thereof at a desired elevation with respect to the ground surface to be paved to control the amount of paving material passing thereunder and thereby to initially form the material generally as a slab of the desired thickness, and then followed by a substantially horizontally disposed undersurface, commonly referred to as a screed, for purposes of leveling and finishing the concrete material. 
     In basic operation, a continuous supply of concrete or other suitable paving material is deposited in front of the paving machine between its transport assemblies as the machine is driven over the intended path of the pavement surface, with the auger mechanism initially distributing the paving material laterally, after which the lower edge of the plate “strikes off” a rough slab form of a desired thickness of the concrete material which then is more precisely spread, leveled and finished by vibration devices followed by the screed. 
     Once such a paving machine is under operation, it is a relatively simple matter to maintain ongoing operation on a substantially continuous basis, absent any malfunctions in the machinery itself, merely by maintaining a sufficient supply of concrete in front of the advancing machine. However, the initial start-up of a paving operation, including beginning operation at the start of each work day or otherwise after a period of sufficiently extended inactivity in the paving operation by which the concrete of a previously paved section of roadway has solidified and begun to cure, requires special efforts and can be much more problematic. 
     Specifically, the initial start-up of a slip-form paving operation, especially when continuing the paving of a previously formed section of pavement, requires that a sufficient starting supply of concrete be deposited not only in front of the auger mechanism and the strike-off plate but also therebehind beneath the screed fully up to the previously formed section of pavement, so as to ensure that there will be no interruption in the continuity nor the quality of the pavement slab. Generally, the only reliable way of accomplishing start-up of a slip-form paving machine under such circumstances is to position the machine immediately above the previously formed section of pavement and then to have workers manually shovel and preliminarily level a sufficient quantity of new wet concrete beneath and behind the auger mechanism, the strike-off plate and the screed, in addition to depositing a supply of concrete in front of the auger mechanism, whereupon operation of the machine can begin. This process is not only labor-intensive, time-consuming, expensive and inefficient, it is also difficult to ensure that the starting portion of the new section of pavement is of comparable quality and uniformity to that of the previously-formed section. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the present invention to provide an improved slip-form paving apparatus which will address and overcome the disadvantages of the known paving apparatus as discussed above. More particularly, it is an object of the present invention to provide a slip-form paving apparatus which will better facilitate the deposition of a supply of concrete beneath the apparatus for starting up a new paving operation. 
     Briefly summarized, the present invention is basically applicable to any slip-form paving apparatus having a frame supported on a steerable self-propelled transport arrangement with a pavement forming assembly or like means disposed on the frame at a forward side thereof. In accordance with the present invention, the pavement forming assembly is movable with respect to the frame between an operative position disposed relative to a ground surface to be paved for distributing and forming a paving material on the ground surface generally into a desired form of pavement and an inoperative position disposed at a greater elevation relative to the ground surface than in the operative position for permitting access beneath the frame during an initial start-up of the apparatus so as to enable a starting quantity of the paving material to be readily deposited thereat. 
     In a preferred embodiment, the pavement forming assembly comprises a spreading mechanism or like means for distributing paving material across the forward side of the frame, e.g., an auger mechanism, a plow-type spreader, or the like, and a strike-off member or like means for generally leveling the pavement material on the ground surface. The spreading mechanism and the strike-off member, such as a strike-off plate, are integrally mounted pivotably to the frame for pivoting movement between the inoperative and operative positions. Thus, with the pavement forming assembly pivoted or otherwise moved into its inoperative position, workers have ready access to deposit and preliminarily work a starting supply of concrete or other paving material beneath the paving apparatus behind the normal operative disposition of the spreading mechanism and the strike-off member, after which the pavement forming assembly may be pivotably moved into its operative position for beginning the paving operation. 
     Other details, features and advantages of the present invention will be described and understood from a detailed description of a preferred embodiment of the invention set forth below with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a slip-form paving apparatus equipped with a retractable pavement forming assembly in accordance with the present invention, illustrating the pavement forming assembly in operative disposition; and 
     FIG. 2 is another front perspective view of the slip-form paving apparatus of FIG. 1, illustrating the pavement forming assembly in retracted disposition. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the accompanying drawings and initially to FIG. 1, a self-propelled slip-form paving apparatus in accordance with the present invention is indicated in its totality at  10 . The paving apparatus  10  basically comprises a structural framework  12  supported substantially horizontally on four front and rear steerable transport assemblies  14 ,  16 , each preferably comprising a so-called crawler assembly of the endless track type, disposed at the four corners of the structural framework  12  in laterally and longitudinally spaced relation to provide stable suspension of, and steering control for, the framework  12 . An internal combustion engine (not shown) or other suitable self-contained power generator, preferably in conjunction with a hydraulic pump (also not shown), is mounted to the structural framework  12  to provide drive power to and steering control of the transport assemblies  14 ,  16 , and to otherwise supply operational power to the various systems of the paving apparatus. 
     The embodiment of the paving apparatus  10  depicted in the accompanying drawings is particularly adapted for use in road construction for the continuous slip-form paving of a slab-type concrete roadway, the lateral width of the apparatus  10  between the front and rear transport assemblies  14 ,  16  being sufficient for the formation simultaneously of two road lanes side-by-side one another. However, as those persons skilled in the art will understand, the essential features and inventive concepts forming the present invention are equally well-adapted to substantially any other form of self-propelled slip-form paving apparatus. 
     The paving apparatus  10  is equipped with a screw-type auger assembly  18  transversely spanning the framework  12  at the forward leading side thereof, comprised of two aligned auger sections  18 A,  18 B each of which is selectively driveable in opposite rotational directions independently of the other auger section, for laterally distributing a supply of concrete, or another suitable flowable paving material, deposited in front of the apparatus across the ground structure over which the roadway is to be paved. However, as those persons skilled in the art will recognize, other types of mechanisms for spreading the paving material may also be utilized instead of the auger assembly, e.g., a plow-type spreader or the like. Immediately rearwardly of the auger assembly  18 , a vertically disposed plate  20 , commonly referred to as a strike-off plate, is supported by the framework  12  with a lower edge  20 A of the plate  20  extending laterally across substantially the full width of the apparatus  10  at an elevation essentially corresponding to the desired elevation to which the roadway slab is to be paved, to act as a metering gate controlling the level of concrete material passing underneath the strike-off plate  20 . 
     A series of vibratory devices, only partially visible at  22  in FIG. 1 but more fully shown in FIG. 2, are mounted to the framework  12  at regular spacings across the transverse width of the paving apparatus  10  immediately behind the strike-off plate  20  to further assist in the leveling and settlement of the distributed concrete material by imposing a rigorous vibratory action on the concrete material passing under the strike-off plate  20 . A finish screed  24  is disposed rearwardly of the vibratory devices  22  and is preferably in the form of a substantially horizontal plate extending transversely across the width of the paving apparatus  10  and rearwardly from the vibratory devices  22 . 
     Thus, the basic operation of the paving apparatus  10  will be understood. As the paving apparatus  10  is self-propelled via the front and rear crawler assemblies  14 ,  16  on the ground surface over which the roadway slab is to be formed, a suitable supply of concrete is maintained continuously in front of the auger assembly  18 . The operator of the paving apparatus  10  actuates and deactuates one or both of the sections  18 A,  18 B of the auger assembly  18  in either direction as necessary to distribute the concrete material with general uniformity laterally across the forward side of the paving apparatus. As the paving apparatus  10  advances, the vertically-disposed plate  20  strikes off a limited amount of the concrete material and partially compacts it to a uniform density, following which the vibratory devices  22  serve to expel any air bubbles from the concrete material and to further settle and smooth the upward surface of the concrete material. As the paving apparatus  10  continues to advance forwardly, the screed  24  is then drawn over the vibrated depth of the concrete material, performing a final compacting thereof and smoothing of its upper surface. 
     To the extent thus far described, the basic structure and operation of the paving apparatus  10  is essentially conventional. As already described above, it will be recognized that the operative disposition of the auger assembly  18  and the strike-off plate  20  substantially closes off access to the underside of the paving apparatus  10  and makes difficult the delivery, manually or otherwise, of a suitable quantity of concrete or other paving material underneath the apparatus for start-up purposes. 
     Accordingly, the present invention deviates from the structure and operation of conventional paving apparatus by mounting the strike-off plate  20  pivotably to the forward side of the framework  12  for selective retraction of the strike-off plate upwardly away from its normal operative disposition. Specifically, a laterally-extending support member  26  is supported from an elevated forwardly-facing portion  12 A of the framework  12  by two crank arms  28  affixed rigidly to the support member  26  at a spacing therealong and, in turn, pivotably affixed to correspondingly spaced support brackets  30  on the frame member  12 A. The strike-off plate  20  is rigidly affixed to the support member  26  for depending relation therefrom in its operative disposition via a pair of bracket arms  32 . Pivoting movement of the support member  26 , the crank arms  28 , the bracket arms  32 , and the strike-off plate  20  about the pivot axis P is controlled via extension and retraction of a linear actuator  34 , preferably in the form of an hydraulic piston-and-cylinder assembly  34  the cylinder body of which is mounted at an elevated disposition on the framework  12  via an upstanding mounting bracket  36 , with the piston extending downwardly to a point of affixation to one of the bracket arms  32 . 
     Additionally, in accordance with the present invention, the auger assembly  18  is affixed integrally with the strike-off plate  20  via a pair of support arms  38  extending forwardly in spaced facing relation to one another from the opposite lateral ends of the strike-off plate  22 , and an intermediate support bearing  40  disposed midway therebetween. Each support arm  38  carries an hydraulic motor  42  from which a respective one of the auger sections  18 A,  18 B extends in alignment with the other auger section to the intermediate support bearing  40  to which each of the auger sections  18 A,  18 B is rotationally mounted. 
     The operation of the present invention may thus be understood. As a result of the mechanical arrangement described above, the auger assembly  18 , the strike-off plate  20 , the bracket arms  32 , the support member  26 , and the crank arms  28  are rigidly affixed with respect to one another for pivoting movement as a unit relative to the pivot axis P defined by the two brackets  30 . With the piston-and-cylinder assembly  34  fully extended, the auger assembly and the strike-off plate unit  20  is pivoted downwardly in its normal operational disposition wherein the auger assembly  18  and the strike-off plate  20  face forwardly from the paving apparatus  10  in relatively close adjacency to the ground surface on which the paving apparatus  10  is supported, so as to operate in the normal manner already described above to distribute, compact and preliminarily level concrete material deposited in front of the paving apparatus  10  as it advances, as illustrated in FIG.  1 . However, upon full retraction of the piston-and-cylinder assembly  34 , the unit of the auger assembly  18  and the strike-off plate  20  is pivoted approximately 90 degrees upwardly and then rearwardly to dispose the auger assembly  18  and the strike-off plate  20  at a substantial elevated spacing from the ground surface and thereby exposing the vibratory devices  22  and the screed  24  to ready access by workers, as illustrated in FIG.  2 . 
     Thus, with the auger assembly  18  and the strike-off plate  20  in the inoperative disposition of FIG. 2, the ability of workers to quickly and easily deposit a start-up supply of concrete, or other paving material, beneath and forward of the screed  24  behind the normal operating disposition of the auger assembly  18  and the strike-off plate  20  is greatly facilitated and simplified. Preparation of the paving apparatus  10  for beginning a new paving operation, whether at a new paving location or continuing from the terminal point of an ongoing paving operation can be accomplished with less labor and in a shorter period of time and, hence, more efficiently and less expensively than with conventional paving apparatus. Once the appropriate start-up supply of concrete has been deposited beneath the paving apparatus  10 , the auger assembly  18  and the strike-off plate  20  are pivoted downwardly as a unit into their normal operative disposition via extension of the piston-and-cylinder assembly  34  to begin the paving operation. An additional benefit of the present invention is that the overall width of the paving apparatus is reduced with the auger assembly  18  and the strike-off plate  20  pivoted upwardly into the inoperative position, which achieves a narrower configuration to better facilitate over-the-road transport of the apparatus. 
     It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.