Patent Grant
8621817
The following is a tabulation of some prior art that presently appears relevant:
This invention discloses a method of casting concrete walls, columns and other vertical or sloped structures using a vertically oriented vibrating screed and utilization of the thixotropic properties of wet concrete. The vertical screed is a simple, inexpensive and highly flexible apparatus that may be used for a wide variety of applications and may be either a hand held or mechanically controlled device. By using a highly thixotropic cementicious material such as concrete, the vertical screed is able to place concrete and other cementicious materials in a vertical plane much like concrete is placed with vibrating screeds in the horizontal plane.
Vibratory screeds are well known in the art for spreading wet concrete in horizontal casting applications such as roads, sidewalks and floor slabs. These screeds are simple devices that have a vibrator attached to a metal plate or tube and are moved horizontally to spread, level and consolidate the wet concrete placed ahead of their forward movement. These screeds are inexpensive, easy to use and come in a variety of sizes and features. However, such a simple vibrating screed does not exist for casting concrete vertically to build a vertical structure.
Walls and other vertical concrete structures have been built with cast-in-place concrete either by using forms, into which wet concrete is cast, or by shotcrete—the spraying a concrete mix against a form backboard. In the case of forms, the wet concrete is placed, vibrated and left to set or harden inside the forms. In some forming systems the forms permanently remain in place while in other systems the forms are removed at some point after the concrete has sufficiently hardened. In those systems where the forms are removed, some are removed after a day or two while in other systems the forms are moved in a matter of minutes which is a process known as slip forming. In most slip forming processes and in the shotcrete process the finished concrete is exposed well before it reaches its final set.
In the slip forming process forms are moved by being “slipped” along the freshly placed concrete and thereby exposing the concrete within a matter of minutes or hours after being cast. This may be done in either a horizontal or a vertical movement and the prior art discloses either one or the other but not the flexibility to switch from a horizontal to vertical movement as may be desirable from application to application. In addition, the slip form prior art are also highly inflexible apart from casting a specific type of wall within limited dimensions and shapes. For example an apparatus capable of casting a tapered road barrier wall is incapable of casting a tall and thin building wall.
There is no prior art that is capable of casting a wide variety of vertical structures ranging from thin walls to thick columns and irregular shapes. There is no prior art that can vary the thickness of the cementicious material applied to these structures and ranging from a thin coating to a reinforced concrete thickness of 24″ or more. Moreover there is no slip form prior art flexible enough to cast composite structures such as insulated concrete walls and that can also be used to apply concrete to thin shelled, ferrocement structures. Nor is there any prior art slip forming apparatuses with the flexibility to cast from only one-side or from multiple sides or in a sloped position in order to cast vertical walls, columns and sloped roofs.
The prior art slip forming systems for casting building walls are large, expensive and cumbersome forming machines or systems with a multitude of jacks or winches. Most of the prior art requires two or more forms that must be used in unison and further require either applying pressure to the concrete, utilizing accelerators for rapid hardening or keeping the forms in place for a short period of time to allow the concrete to set. In addition, the prior art that discloses slip forms for road barrier walls depend, primarily upon casting short and stocky or taller tapered walls and it is the wall's profile that enables the wet concrete to retain its shape as the slip form passes by.
None of the prior art discloses a reliance upon the thixotropic properties of no-slump concrete as a basis to the concrete retaining its shape as the slip form passes by. And none of the prior art can be downsized to an inexpensive hand held apparatus that can perform the same functions as a much larger mechanically operated apparatus.
The prior art slip forms that are based upon a one-sided forming system either require the cementicious material to sufficiently hardened before the forms are moved or uses the shotcrete process. The shotcrete process of placing concrete uses air pressure and a gun or nozzle to impinge wet concrete in thin layers against a vertical form/backstop with successive layers built-up to the desired thickness. The thin layers and air pressure dissipates most of the hydrostatic pressure that is ordinarily created with vertical stacking of wet concrete. The result is minimal sagging and the ability to hand trowel it to a smooth, vertical surface within minutes after the final layer has been applied. Shotcrete is a more expensive system due to the material waste caused by the rebounding sprayed concrete, safety precautions related to a spraying operation and the hand labor required to work the sprayed concrete into an acceptable finish.
While there is no prior art of vertical vibrating screeds, there are vibrating trowels that are used to finish either vertically or horizontally placed concrete. The vibrating trowels do not place the concrete or vibrate the full depth of the concrete, but rather vibrate the surface area to produce a better finish and appearance.
The present invention is a simple, low cost and highly flexible alternative to slip forms and shotcrete. It can be used to cast any type, size and shape of solid or composite vertical or sloped concrete structure. In its most simplified design, the present invention is a small, inexpensive handheld vibrating screed that places, consolidates, shapes and finishes concrete or other cementicious material in a vertical manner so as to construct building walls or to apply a thin coating to a wall or other vertically oriented structure. In its more elaborate design, the present invention does these same activities, although in a larger and highly mechanized apparatus. Such a large mechanical device can place hundreds of square feet of area per hour to build walls, columns and other vertical structures or place concrete on roofs, embankments and other sloped structures.
The present invention is able to screed concrete vertically while being vibrated because it utilizes the thixotropy of low-slump concrete. Thixotropy is a material property that describes a material as being in a solid state when at rest and becoming liquefied while being agitated. Thixotropy is a property of freshly mixed zero-slump, no-slump or low-slump concrete in that this type of concrete is in a solid state, similar to moist, clumpy dirt, when at rest and becomes liquefied when vibrated. Therefore, concrete and other cementicious materials with a zero-slump, no-slump or low-slump are said to be highly thixotropic. Relative to the present invention, this material property enables the no-slump or low slump concrete to be consolidated, spread, shaped and molded in a liquefied state through vibration by the screed and then to immediately revert to a solid state once the vibration ceases as the moving screed passes by. When in a solid state, the no-slump, concrete exerts no hydrostatic pressure which enables it to hold its shape while other wet concrete is being stacked vertically above it, no matter what the wall height or thickness.
An important aspect of this invention is that it is the only concrete placing machine that enables concrete to be inexpensively placed in a vertical plane much like concrete is inexpensively placed in a horizontal plane. In both applications, a vibrating screed liquefies, consolidates, spreads and levels the fresh concrete against a stay-in-place or removable form. The primary difference is at the concrete used in the vertical application must have a high degree of thixotropic behavior that is found in low or no-slump concrete whereas the concrete used in horizontal castings typically uses a much higher slump of concrete. This difference in the concrete slump requires certain modifications to the vibration to ensure the no-slump concrete is adequately consolidated, shaped and finished.
In one embodiment of this invention, the vibrating screed is vertically oriented and is used to place highly thixotropic concrete, in a vertical plane to cast walls, columns and other vertical structures in a wide variety of thicknesses, shapes and sizes.
In another embodiment of this invention the vertical screed is a simple, inexpensive and highly flexible apparatus that can be configured for use as either a small hand held device or a larger, mechanically operated apparatus capable of placing several hundred square feet of area per hour.
In another embodiment of this invention, the vertical screed may be mounted on tracks or a mechanical arm and used to stabilize and move the screed in a vertical, horizontal or diagonal direction.
In another embodiment of this invention, sensors and other mechanical or manual means are used to guide the vertical screed in a predetermined path and apply the appropriate thickness of material needed for a particular application.
In another embodiment of this invention the vertical screed is used to place concrete to cast a sloped structure such as a sloped roof or embankment.
In another embodiment of this invention, the vertical screed has a degree of flexibility that it can be used to place concrete on one side of a vertical structure such as a composite wall or on multiple sides of a vertical structure such as a column.
In another embodiment of this invention a mesh is used to support the cementicious material and the use of several layers of wire mesh enables the construction of thin walled ferrocement structures by using this invention.
In another embodiment of this invention additives may be added prior to or during the placement of the cementicious material to achieve a variety of desired effects.
Other objects, advantages and features of my invention will be self evident to those skilled in the art as more thoroughly described below.
The present invention discloses a method of casting concrete walls, columns and other vertical structures or sloped structures such as roofs, by use of a vertically oriented screed and utilization of the thixotropic properties of wet concrete. Freshly mixed concrete and other cementicious materials that have a zero-slump, no-slump or low-slump all contain a high degree of thixotropy and are thereby highly thixotropic. Throughout the following detailed description the term low-slump concrete shall include zero-slump and no-slump concrete and shall also refer to other highly thixotropic cementicious materials. In addition, the term vertical shall include anything sloped so that a vertical structure includes a sloped structure such as a sloped roof and vertically oriented includes a slope.
As the vertical screed 10 is moved, the concrete 11 falls from the hopper 14 into the casting area 26 and against the form 12 that provides a backstop, and fills the casting area 26 between the screed face 15 and the form 12. Once the low-slump concrete 11 is in the casting area 26, it is vibrated by a vibrator 20 attached to the backside of the screed face 15 as a means for liquefying, consolidating and spreading the concrete 11 to fill the casting area 26 between the screed face 15 and the form 12.
The vertical screed 10, with its screed face 15 and vibrator 20 acts to liquefy, consolidate and spread the low-slump concrete 11 against the form 12 and around the steel reinforcement 19 to produce a solid concrete structure with an outside face 17 of a concrete wall 18. Immediately below the vertical screed 10 is a slip-form 16 that extends and finishes the forming function of the screed face 15. The slip form 16 is in the same plane as the screed face 15 and does not vibrate or has minimal vibrations so as to allow the recently cast low-slump concrete 11 to revert to its solid state while retaining the shape produced by the screed face 15. The slip form 16 provides the concrete 11 a transition from its liquefied state, as caused by the intense vibrations on the concrete 11 produced by the screed face 15, to its exposed, unsupported and finished solid state. The slip form 16 also provides the desired finish to the outside face 17 and may be directly or indirectly attached to the vertical screed 10 or it may be a separate device that trails the vertical screed 10.
One embodiment of the invention is to utilize the thixotropic properties of low-slump concrete. Thixotropy is a material property that describes a material that is in a solid state when at rest and a liquid state while being agitated. The thixotropic property of freshly mixed low-slump concrete is such that it is in a solid state after mixing, liquefies during vibration and immediately reverts back to a solid state when the vibration ceases. Specifically, upon mixing and during placement, the low-slump concrete is similar to moist clumpy dirt and, as it is vibrated by the screed, it is liquefied into a cookie dough-like material that flows and fills the contained space. When vibration ceases, the concrete immediately reverts back to its solid state, which is now a consolidated, shaped and solid structure. In addition, the low-slump concrete exerts little or no hydrostatic pressure when in its solid state which enables it to hold its post-vibration shape despite additional wet concrete stacked on top of it. Additives may be added to the concrete and/or heat, pressure or other mechanical means may by used by the vertical screed 10 or form 12 to induce an even faster set time.
In one embodiment the means for liquefying, consolidating and spreading the concrete is caused by directional vibrations extending from the screed face 15 into the adjacent concrete 11 and continuing through the concrete 11 until reaching the form 12 against which the concrete 11 is vibrated. The concrete 11 cast into the casting area 26 is vibrated to liquefy, consolidate and spread only within the casting area 26. There are a variety of directional vibrators that may be attached to the screed face 15 and are well known in the art.
While the entire screed face 15 vibrates, the vibrations may be stronger at some locations and less or even minimal in others. For example, the vibrations at the bottom of the screed face 15 may be minimal so as to facilitate the transition of the concrete from the screed face 15 to the trailing slip form 16 or the slip form 16 may be a non-vibrating or minimally vibrating area of the screed face 15.
In addition the vibrations at the top of the screed face 15 may have a different amplitude or frequency than the vibrations at the bottom of the screed face 15. This could be accomplished by having vertically stacked directional vibrators attached to the screed face 15 (not shown) A frame 25 as shown in
Also shown in
Also shown in
In another configuration of this invention one or more variable speed vibrators may be used to increase the flexibility of the invention. For example one vibrator of a multi-vibrator screed may be set to produce a high amplitude and/or frequency to vibrate a deeper area of a wall while an adjacent vibrator may be set with lower amplitude and/or frequency to vibrate a much thinner adjacent wall section. In addition, the seam form 22, edge barrier 23, hopper 14 and slip form 16 may be disconnected from the vertical screed 10 to provide it with greater flexibility to place and finish the concrete. For example the vertical screed 10, after disconnecting some or all of the above parts, may be used as a vibrating trowel to work the surface area of the vertical structure or fill concrete into small voids.
The screed face 15 may have a flat, concave or convex surface or it may have a moving object built into it so as to shape the concrete 11 as the screed face 15 passes by. The screed face 15 may also be three dimensional with curved or rectangular shapes as shown in
To cast a wall, column or similar vertical structure, a vertically oriented backstop is positioned on one side of the casting area 26. The backstop is a surface against which the concrete is cast and vibrated or otherwise liquefied, consolidated and spread by the vertical screed 10 and its vertically oriented screed face 15 positioned opposite the backstop, on the other side of the casting area 26. The backstop may be a form 12 and may be either a stay-in-place or a removable type. For example in
The hand held configuration of the vertical screed 10 is shown in
The vertical screed 10 may be used vertically as shown in
As a means for supporting and guiding the vertical screed 10 in a predetermined direction while maintaining a predetermined distance from the from 12, it may be hand held or it may be mechanically supported and guided by one or more tracks or other mechanical means including cables, mechanical arms, cylinders and platforms.
The vertical screed must be guided in terms of both its direction and in maintaining a predetermined distance between the vertical screed and the form. The means for supporting and/or guiding the vertical screed in this manner may be done manually or mechanically with tracks or a mechanical arm and may include the use of a sensor 24 as shown in
In another configuration, the vertical screed 10 and hopper 14 may be mounted on one or more tracks 51 and intermittently repositioned to place the concrete 11. For example, instead of placing concrete 11 in a continuous directional movement, the vertical screed 10 and hopper 14 may be held in a predetermined location while the concrete 11 is placed and once that location is fully placed, then the vertical screed 10 and hopper 14 are repositioned to the next location for concrete placement and repeating the process.
The vertical screed 10 apparatus may also have horizontal tracks 52 as shown in
To obtain finished and well compacted corners or edges, top forms 40 and edge forms 41 may be placed at the outside and top corners or edges and at the window, door and other openings.
The present invention may also be used in a configuration that has a slip form or a second vibrating screed as the backstop instead of the form 12.
Frames 25A and 25B may be moved separately or together and manually or mechanically with winches, cylinders, screw, cogs, crank or other means know to the art. For example a single hoist may be used to raise both sides or separate hoists may be used to raise each side. In addition, the two tracks 51A and 51B and their respective support frames may be connected at the top or sides or they may be totally separated as may be desirable in certain situations.
In addition to being a second slip form 58, the backstop of this invention may also be any apparatus that affects the concrete from the second side of the vertical structure. For example the backstop may provide heat to speed the concrete setup and curing or a packing mechanism that packs the concrete from one side while it is vibrated from the other side of the wall or column.
The hopper 14A is also optional and as an alternative the concrete 11 could be cast directly into the casting area 26 between the two vibrating screeds 10A and 10B. The purpose of the hopper 14A is to cast the concrete 11 into the casting area 26 and in some applications the width of the casting area may be sufficiently large to eliminate the need for a hopper.
Another embodiment of this invention is its high degree of flexibility in casting a variety of types, sizes and shapes of vertical structures. In addition to straight walls, columns of all shapes and sizes can be cast from the vertical screed of this invention. For example, one or more vertical screeds 10 may be positioned on one or more sides of a column with or without forms 12 set opposite or between the screeds. When done without forms 12, the vertical screeds 10 opposite one another provide another means for providing the backstop.
In all of the above configurations, the concrete vibration was caused by a vibrating screed that is well known in the art as an external vibrator. In another configuration of the invention, the concrete vibrations are caused by an internal vibrator which is also well known in the art.
The internal vibrators 56 may be mounted anywhere on the vertical screed 10 or support frame or on another mechanical apparatus or they may be manually held and used to consolidate the concrete or otherwise work in concert with the slip forms which acts to shape and texture the concrete in this configuration.
In another configuration of the invention, a cylinder 57 is situated above the concrete and used to deposit, consolidate and spread the concrete 11. The cylinder 57 may simply spin or it may also vibrate or otherwise agitate the concrete. The cylinder 57 may also have protrusions that extend into the concrete (not shown).
There are any number of additives that can be used with the concrete and the invention. For example, the additives can be used to lubricate the concrete, as a water reducer or to induce a fast set. The additives may also be added to the concrete mix or injected, sprayed or otherwise applied to the concrete at any time prior to, during or after the vertical screed has placed the concrete.
The vertical screed may be designed such that it performs more than one function as it passes by the concrete. For example the top section of the screed may provide the vibration stage whereby the concrete is liquefied and consolidated. The lower part of the vertical screed or an attachment thereto may provide a second stage such as a mechanical device that packs the concrete and a third part of the screed may act as a slip-form to shape the concrete. Other functions that may be used with the vertical screed include: mixing concrete, placing additives, heating or dehydration and applying concrete finishes.
In another configuration of this invention, wire or plastic mesh or similar materials may be used to support the wet concrete in its vertical position while curing or to construct ferrocement structures.
Additionally, the mesh 60 may be a wire mesh and set in a multitude of layers so as to produce a ferrocement structure when the concrete is applied to it. In this manner, the vertical screed can be used to cast a wire mesh reinforced thin walled concrete structure as is well known in the art.
In
In this configuration the screed face 15 is positioned perpendicular to the ground and parallel to the face of the wall or column being cast with the cementicious material. The only difference is that the vertical screed has been rotated 90 degrees to an upright position so as to more efficiently place the concrete when used in a horizontal direction.
The vertical screeds may be configured to be field modified for use in either the vertical direction or in the horizontal direction. When the same vertical screed used in the vertical direction is modified for use in the horizontal direction, the vertical screed and hopper are rotated 90 degrees. This causes the top and one side of the hopper in the vertical direction to change positions when used in the horizontal direction. Therefore, what used to be the open top of the hopper in the vertical direction is now the side of the hopper in the horizontal direction and must be closed to prevent the concrete from falling out of the hopper. Likewise, what was the closed side of hopper in the vertical direction is now the top of the hopper in the horizontal direction and must be opened to allow concrete to be fed into the hopper.
From the above it is apparent that the vertical screed can also be moved in a diagonal direction as the application may require or otherwise may be desirable.
From the description above, a number of advantages of some embodiments of my vertical screed and method of casting vertical structures with a vertical screed become evident:
Although the description above contains many specifications, these should not be construed as limiting the scope of the embodiments but as merely providing illustrations of some of several embodiments. Thus the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given.
This application claims the benefit of the filing date of U.S. Provisional Application Nos. 61/458,934 filed Dec. 3, 2010 and 61/461,436 filed Jan. 18, 2011, both incorporated herein by reference.
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