Method and apparatus for precision slip-forming of complex precast shapes

BACKGROUND

1. Field of Invention

2. Prior Art

Prior art molding and casting techniques are not well suited to the need to produce economical and precise large concrete module structures. There is a need for a method to cast precision parts of complex geometry repeatedly and quickly.

U.S. Provisional Patent Application No. 60/417,065 and utility patent application Ser. No. 10/680,939 by applicant for “Method and Apparatus for Precast and Framed Block Element Construction” describe a LadderBlock™ modular concrete construction apparatus and method, and are incorporated by reference herein.

SUMMARY OF INVENTION

Inventive methods are presented here for the rapid precision forming of complex precast shapes. In one embodiment, reinforced concrete is utilized to build structural blocks which are manufactured structural parts. These blocks might also be of any other structural grade, castable material that is properly engineered and reinforced to ensure safety under load. These methods result in cast parts that can be held to a dimensional tolerance that is unexpected in the construction of conventional concrete structure. The benefits of precision concrete construction are found in ease and speed of fit-up and in a novel architectural aesthetic. There is a beauty in precision that is naturally pleasing to the human eye, but precision can be hard to find in most conventional construction.

In one embodiment, a slip-form table is provided that enables the rapid replication of identical parts without form disassembly and with relatively little effort as compared to conventional construction practices. It is a production tool that can be revved up to meet demand and to economically produce strong, durable, and beautiful structure.

The Challenge

U.S. patent application Ser. No. 10/680,939, by applicant hereinafter referred to as LadderBlock™ presents a method for producing these complex structural blocks using steel forms separated by steel pipe sleeves. While this method is valid and useful, it does involve a multitude of steel assemblies whose connections must be loosened in order to strip the forms after each casting cycle. Those same connections would need to be drawn tight prior to casting the next block. Steel assemblies that form enclosed spaces between the chords of a block must collapse inward, or risk being forever bound in the cast block. Connections between steel forming components would therefore need to be slotted, two-position connections, but slotted connections present an opportunity for a worker's error to degrade the precision of the cast block during every casting cycle. Because any deformation of the steel forms during casting would also degrade the precision of the block, steel form components must be stiff; this can result in a very heavy steel section if the form is required to span a significant distance along the edge of a large block. Steel assemblies in a water-laden casting environment must be protected against corrosion or they will rust away.

A substantial effort is required to maintain steel forms and to loosen and tighten all of those connections, but the potential loss of precision could be even more expensive. These considerations combine to indicate a compelling need for a forming system that is dimensionally stable, stiff, and durable, and that requires no disassembly or reassembly in the repetitive production of precision blocks. Such a forming system is presented herein.

The Solution

FIG. 1 shows one embodiment of a slip-form table system 100 that forms and then extrudes partially cured precision blocks, from simple to long and complex structural shapes. One key feature of this system is the slip-form assembly 200. This assembly consists of a sheet-metal or other replaceable forming face 220 that is backed up by a layer of rigid insulation or other suitable compressible backing material 240 (not shown), which is in turn backed up by a rigid slip-form table structure 300. Although the table structure could be of steel or other construction, one embodiment features a table structure that is itself a reinforced concrete casting. This construction minimizes maintenance and maximizes the durability and dimensional stability of the table.

The table is, in essence, an operable structure of match-cast parts that may be driven by threaded rods or other mechanical means at a series of lift points. It may be hand-driven by a group of workers using standard wrenches, one at each lift point, or it may be or may be mechanically driven such as by a set of impact wrenches or by an electric motor connected to a chain and sprocket or gear drive system. The operation may also be driven by hydraulics, air rams, air bags, or another suitable mechanical drive system. The threaded-rod drive of the embodiment presented offers a cost-effective opportunity to simultaneously drive all lift points upward or downward, and it can be operated under human power if necessary. The threaded-rod drive also allows the slip-form table to be used as a concrete press that can minimize troweling and allow the stamping of architectural patterns, or a functional feature such as a pipe chase, in the flat faces of a block.

Beyond the production of LadderBlock™ structural shapes, a slip-form mechanism may be used to produce a wide variety of structural and architectural components. These are not limited to but could include shell and plate components such as folded-plate partition walls, shower enclosures, furniture components, and match-cast segmental structures. A slip-form could be scaled up or down to make components of a variety of sizes, configurations, and uses that may extend far beyond the structural and architectural arena.

DESCRIPTION OF FIGURES

FIG. 1A is a top perspective view of a slip form table with a recessed molding area formed by a slip form.

FIG. 1B is a top perspective view of the slip form table of FIG. 1A with a cast part.

FIG. 2 is a top perspective view of a simple slip form for the slip form table of FIG. 1A.

FIG. 3 is a top perspective view of a lift master for the slip form table of FIG. 1A.

FIG. 4 is a top perspective view of a leg and tie-down system for the slip form table of FIG. 1A.

FIG. 5 is a top perspective view of a drive mechanism for the slip form table of FIG. 1A.

FIG. 6A is a top perspective view of a complex slip form.

FIG. 6B is a top perspective view of a slip form table with the complex slip form of FIG. 6A.

FIG. 7A is a top perspective view of a LadderBlock module 1000 assembled from is basic chord elements 1001-1010.

FIG. 7B is a top perspective exploded view of a LadderBlock module 1000 showing its basic chord elements 1001-1010.

FIG. 8 is a top perspective view of the basic chord elements 1001-1010 of FIG. 7B bound together on a casting surface to form the concrete master, and inner and outer forms that are required to cast the entire slip-form.

FIG. 9 is a top perspective view of match-drilled long steel channel pairs with through-bolt holes to set the channels at a desired width for casting chord sections.

FIG. 10A is a top perspective view showing a desired angled end section 1070 and a desired straight end section 1080 for a chord element.

FIG. 10B is a top perspective view showing individual steel plate members 1071-1076 which are required to form angled end section 1070, and steel plate members 1081-1086 which are required to form straight end section 1080

FIG. 11 is a top view of a steel plate with a plurality of steel plate members laid out on the plate.

FIG. 12 is a top perspective view showing the ends of master blocks 2000 and 2002 bound together with threaded-rod pipe clamp 2010.

FIG. 13 is a top perspective view showing top assembly clips 2020, 2021 and bottom assembly clips 2030, 2031

FIG. 14 is a top perspective view showing the top assembly clips 2020, 2021 and the bottom assembly clips 2030, 2031 placed over the ends of master blocks 2000 and 2002

FIG. 15 is a top perspective view showing the top assembly clips 2020, 2021 and the bottom assembly clips 2030, 2031 binding a slip-form assembly 2040 to the faces of the master block 2000 and 2002.

FIG. 16 is a top perspective exploded view of a slip-form assembly 200 with forming faces 220, compressible backup 240, and nailers 250.

FIG. 17 is a top perspective view of a portion of a slip-form table system 100 showing vertical pipe sleeves 350.

FIG. 18 is a top perspective view of a slip-form table system 100 which is ready to cast, showing reinforcing steel 400, standard lift inserts 420.

FIG. 19 is a top perspective view of the slip-form table system of FIG. 18 after casting, partial curing of the concrete, and removal of the master blocks to reveal the void which will form the precision structural blocks 3000.

FIG. 20 is a top perspective view of a cast monolithic master 3100 with lift beams 3200.

FIG. 21 is a top perspective view of lift beams 3200 interspersed within an array of casting beams 3300 to form a casting bed 3400.

FIG. 22 is a top perspective view of lift beams 3200 showing plinths 3210 and rebar hoops 3220.

FIG. 23 is a top perspective view of an example of lift beams 3200 interspersed within an array of casting beams 3300 to form a casting bed 3400.

FIG. 24 is a top perspective view of a previously cast slip-form 210 laid into position on top of the casting bed of FIG. 23.

FIG. 25 is a top perspective view of the slip-form casting bed of FIG. 24 with packable material 3410 filling the voids within the slip-form below the tops of the lift beam plinths.

FIG. 26 is a top perspective view of the slip-form and casting bed of FIG. blockouts 3420 and reinforcement 3440 installed.

FIG. 27 is a top perspective view of a cast base master 380 with lift beams 390.

FIG. 28 is a top perspective view of the cast base master 380 of FIG. 27 with grouted studs 3460 installed.

FIG. 29 is a top perspective view of a casting form for making a plurality of table legs 3500.

FIG. 30 is a top perspective view of a drive mechanism 3700 comprising a drive rod 3710, a drive housing 3720, and a bottom bracket 3740.

FIG. 31 is a bottom perspective view of a bottom bracket 3740 comprising a steel channel 3742 with its flanges turned down.

FIG. 32 is a top perspective view of a drive housing 3720 comprising a steel channel 3722, a steel plate 3724 with a centered hole, and a short section of steel pipe 3726 welded to it.

FIG. 33 is a top perspective view of a lift master 400 is positioned on a slab 410 on wooden blocks.

FIG. 34 is a top perspective view of biaxial sleeves 3230 installed on the grouted studs 3460 of the lift master 400.

FIG. 35 is a top perspective view of reinforcement 3440 tied to the biaxial sleeves 3230 of FIG. 34.

FIG. 36 is a top perspective view of the lift master 400 and the reinforcement cage 420 it carries lowered into the slip form 210.

FIG. 37 is a top perspective view of a cast block 500 from the slip table of FIGS. 23 to 36.

FIG. 38 is a top perspective view of a multi-stack slip-form 260 with an elevated slip-form table 270.

FIG. 39—outlines the steps in one example for making and using a slip-form table.

FIG. 40 shows one example for the detailed steps for fabricating the slip form table components of FIG. 39.

FIG. 41 shows one example for the detailed steps in assembling the slip form table of FIG. 39.

FIG. 42 shows one example for the detailed steps in operating the slip form table of FIG. 39 to produce cast parts.

FIG. 43 shows one example for the detailed steps in operating a multi-stack version of the slip form table of FIG. 39 to produce cast parts on a shorter casting cycle.

FIG. 44 shows one example for the detailed steps in operating a bottom-harvest, multi-stack version of the slip form table of FIG. 39 to produce cast parts on a shorter casting cycle.

DETAILED DESCRIPTION OF EMBODIMENT—OVERVIEW

FIG. 39 is a flowchart which outlines the general steps in one example for making and using a slip-form table. The steps include fabricating the slip form table components at step 5000; assembling the slip form table at step 5500; and operating the slip form table to produce cast parts at step 5700.

Detailed Description of Embodiment—Slip-Form Table Construction

In this embodiment, the slip-form table comprises four major components as illustrated in FIGS. 2-5. FIG. 2 is a top perspective view of a simple slip form 210 for the slip form table of FIG. 1A. FIG. 3 is a top perspective view of a lift master 400 for the slip form table of FIG. 1A comprising a base master 380 and lift beams 390. FIG. 4 is a top perspective view of a leg 3500 and tie-down 3540 system for the slip form table of FIG. 1A. FIG. 5 is a top perspective view of a drive mechanism 3700 for the slip form table of FIG. 1A.

Slip-Form

While the slip-form itself is a relatively simple casting that presents a void in the shape of the desired precast block, its construction is unique and somewhat complex. For a simple shape, the slip-form is a single casting.

FIG. 6A is a top perspective view of a complex slip form. FIG. 6B is a top perspective view of a slip form table with the complex slip form of FIG. 6A. For a complex part with internal spaces, such as an open web truss as shown in FIG. 6A, the slip-form is built as a match-cast set of components that combine to form the shape of the desired block.

Critical factors driving the design and construction of the slip-form are the desire to have the void precisely define the dimensions of the block, and the need for the vertical forming faces to include a mechanism to allow them to slip vertically after initial curing without binding or damaging the cast block. Precision is obtained using the master block methodology described below, and the slip interface is built using slip assembly clips to hold the slip-form assembly tight against the face of the master blocks during casting. With master blocks and the slip assembly in place, sleeves and reinforcement are installed and the slip-form is cast. Master blocks are then removed to leave the completed slip-form. On the occasion of the construction of a first slip-form of its type, a monolithic master may be immediately cast to enable the layout of future slip-forms for identical parts to be produced without the tedium of master block precision layout and binding; the monolithic master can serve as a template for the production of an unlimited number of consistent slip-forms.

Master Blocks

The approach taken to build the precision slip-form of this example is to build that form around a precise master; with the master essentially acting as an inner form. The material most commonly used in building forms for concrete structure is wood, with steel forms being the second most common construction through their use in the U.S. precast industry and in some commercial construction. Because of the large pressures that develop during the placement and vibration of fresh concrete, forms must be stiff and well-connected. They also must be tied down to resist buoyant pressures that can develop during casting. Bowing of forms, failures of form connections, and blowout of fresh concrete due to uplift of forms are all rather common occurrences in conventional concrete construction, except in cases where the formwork has been engineered and built well. But the production of precision concrete components with wood forms is virtually impossible, because the dimensions of wood can change dramatically with changes in moisture and temperature. Concrete casting creates a wet environment with dramatic temperature swings. Steel is much more dimensionally stable than wood, but if left unprotected it will corrode quickly in such an environment. One dimensionally stable construction material thrives and gains strength in the wet, hot environment of a concrete casting operation—that material is concrete itself. The weight of concrete form components can eliminate the need for tying down forms, and the stiffness of concrete components helps them to retain their shape when subjected to casting pressures. It is for these reasons that concrete was selected as the construction material from which to build the master for each desired geometry of structural block.

Analysis of LadderBlock designs revealed that essentially all of the chord elements that make up each LadderBlock component are prismatic (i.e. constant cross-section) rectangular cross-sections with either square or mitered ends, but with a well-defined termination angle at each end. The approach was thus adopted that each LadderBlock component would be broken down into its basic chord elements as illustrated by FIGS. 7A and 7B. Each of these chord elements 1001-1010 may be produced with precision, and the resulting master blocks may be bound together on a casting surface to form the concrete master 1000 for each part to be produced. Initial tests of this concept were so successful that the master block methodology was adopted as the means of building not only the assembled master of each part, but also the inner form 1020 and the outer form 1030 that are required to cast the entire slip-form as illustrated in FIG. 8.

The originally described manufacturing procedure for LadderBlock, i.e. using a steel pipe bound with a through-bolt between two steel channels to form a precise width, works well for producing such chord elements. In one example, full-length 40 foot long steel channel pairs were match-drilled to ensure precise alignment of through-bolt holes in each channel of the pair. FIG. 9 is a top perspective view of match-drilled long steel channel pairs 1040, 1042 and 1050, 1052 with through-bolt holes 1043, 1053 to set the channels with through-bolt 1060 to a desired width for casting chord sections. This method allows precision width-forming. The precise forming of the square or mitered ends of each master block, and the precise layout of member length between sets of end forms is described below.

In this embodiment, the required precision of square and angled end forms was achieved by first modeling and building each required steel plate end form assembly on the computer, using 3D CADD modeling capabilities. FIG. 10A is a top perspective view showing a desired angled end section 1070 and a desired straight end section 1080 for a chord element. FIG. 10B is a top perspective view showing individual steel plate members 1071-1076 which are required to form angled end section 1070, and steel plate members 1081-1086 which are required to form straight end section 1080.

The modeled plates can then all be laid into the same plane and arranged to maximize the utilization of a standard 5′ by 10′ sheet as illustrated by FIG. 11, and an angle gauge can also be designed for each precise angle that is to be formed. A 2D top view can then be used to write a geometry file, and that file can be transmitted to a shop along with a contract for cutting the required plates. In one example, a 3/16″ thick steel plate 1090 was cut using a high-precision water jet cutter. Other computer-controlled cutting methods are available, but the water jet method produces precision cuts without the plate-deforming heat of other methods. Plates are typically designed with interlocking slots and tabs to facilitate fit-up prior to welding the assembly.

Precision steel end forms solve the end angle challenge, and with the end forms clamped between the channels, the layout and construction of precise master blocks only requires care and multiple layers of dimensional checks prior to casting. Such processes can result in parts that can be held to a dimensional tolerance of plus or minus 1/16 inch. Depending on the length of each block, from one to several master blocks can be produced simultaneously out of each channel pair.

Once all of the required master blocks have been produced to form a LadderBlock part and its inner and outer forms, the blocks can be laid out on a slab, much like a giant puzzle that weighs several thousand pounds. That heft helps the forms resist the forces of concrete placement without moving, but dead weigh alone is not enough. FIG. 12 is a top perspective view showing the ends of master blocks 2000 and 2002 bound together with threaded-rod pipe clamp 2010. FIG. 13 is a top perspective view showing top assembly clips 2020, 2021 and bottom assembly clips 2030, 2031. FIG. 14 is a top perspective view showing the top assembly clips 2020, 2021 and the bottom assembly clips 2030, 2031 placed over the ends of master blocks 2000 and 2002. FIG. 15 is a top perspective view showing the top assembly clips 2020, 2021 and the bottom assembly clips 2030, 2031 binding a slip-form assembly 2040 to the faces of the master block 2000 and 2002.

With a close eye on maintaining dimensional precision in the final master block layout, ends of master blocks are bound together with threaded-rod pipe clamps as illustrated in FIG. 12 in preparation for casting. Before setting the master blocks that form the shape of the LadderBlock part, slip assembly clips are laid out across the top and bottom of the master blocks, as illustrated in FIG. 14, where required to tightly bind the slip-form assembly to each face of the master block. Clips can temporarily be locked into the desired position on a master block using 2″ wide temporary wedges. These prevent free movement of clips while master blocks are being manipulated into their final clamped position and until slip-form assemblies are installed.

Slip Assembly Clips

The slip assembly clip 2020 is a simple fabrication that is designed to allow the slip-form assembly to snap into position and be held tightly against the face of the master block. Clips in this example are simple 3″ wide strips of sheet metal that is bent into a deep “C” profile, and narrow flanges are fabricated with an extension that is bent back toward the web. These extensions are bent further toward the flange by the insertion of the slip-form assembly on both sides of the master block; the bent metal flange of the clip exerts a spring-clamp action of the slip-form assembly when it is installed. Clips are installed at a regular spacing crossing the top and bottom face of each master block, as close as is necessary to ensure that the assemblies are tightly held against the face of the master block.

Slip-Form Assembly

FIG. 16 is a top perspective exploded view of a slip-form assembly 200 with forming faces 220, compressible backup 240, and nailers 250. The construction of the slip-form assembly works with the rigid form structure to make an effective forming system that can be slipped vertically. The forming face could be of sheet membrane, fiberglass, plate steel, or other suitable material, but the forming face in the example embodiment is made of sheet-metal that is bent into a “C” shape, with a deep web bounded by a narrow top flange 222 and bottom flange 224. The forming face may be attached with screws to nailers 250 that are cast into the slip-form structure, and the nailers combine to bind in place the compressible backup, in this case consisting of common insulation board, that covers the web of the forming face. Nailers are first prepared with screws that act as shear studs to permanently attach the nailer to the concrete into which it will be cast.

Ipe′, a Brazilian hardwood, is used in one embodiment because of its dimensional stability and hardiness and because its natural oils seem to make it compatible with the harsh chemical exposure of concrete construction. The nailer could also be of another wood, a composite, or another suitable material. Because it is continuously supported by the form structure, the insulation board creates an effective lateral support for the forming face during casting.

The logic behind the slip-form assembly is straight forward. After casting and initial cure, suction exists between the newly cast part and the forming surface. Without the application of debonding agents prior to casting, the bond between these surfaces might be much stronger. The suction between the parts must be broken in order for the form to slip, and surfaces that are not perfectly parallel risk binding and damaging the form, damaging the block, and/or causing fit-up problems in the field. The insulation board serves to offer some forgiveness to slight variations in verticality. If a cast block face is not perfectly vertical, the compressible backup can yield enough during harvest to allow the block to pass without damage, and without having to disassemble or reassemble the forms. In the case of a bent sheet-metal form face, the compressible backup effectively provides an unsupported space to allow flexure in the flanges of the sheet-metal when the casting surface is pulled vertically by casting suction as the slipping operation begins. It is important that the insulation board or other compressible material be continuous so that the cast slip-form concrete bears only against the insulation board or other compressible filler, and not directly against the back side of the forming face. Otherwise that forgiveness is lost and binding of the forming face between two hard-cast concrete surfaces is risked. The slip-form assembly works very effectively. Upon initiating relative vertical movement between the slip-form and the cast block, the casting surface of the sheet metal moves vertically with the block, and its flanges can be seen to deflect between the top edge of the casting surface and the connection screws. Because the sheet metal is bent at 90 degrees, flexure in the flange must translate into some flexure in the web. Flexure in the web equates to a suction-breaking prying action on the web. The insulation board again permits just enough compliance to allow that prying action to occur, and the assembly can even be heard to pop lightly when suction is broken and the newly cast block breaks free.

Once slip-form assemblies are bound in position on the master blocks using form clips or another method, then the pipe sleeves, reinforcement, and lift inserts may be installed prior to casting the example concrete slip form structure.

Sleeves, Reinforcement & Lift Inserts

FIG. 17 is a top perspective view of a portion of a slip-form table system 100 showing vertical pipe sleeves 3520. In this example, vertical pipe sleeves are designed into each slip-form at each lift point and at each location where a tie-down is required, and a pair of sleeves are provided at each location where a table leg is required. Sleeves provide the required connectivity between slip-form table components and help to hold the structurally required reinforcing steel in the desired position during casting. The sleeves themselves are held in position during casting by vertical grouted studs that extend from the casting surface, similar to the grouted studs that extend from the lift master as described below.

In conjunction with placing and tying the necessary reinforcing steel, standard lift inserts common to the precast industry are set into the top of the form at the locations required for lifting and handling the slip form. The concrete slab and master blocks are then treated with a debonding agent. With these tasks completed, the slip-form is ready to cast. FIG. 18 is a top perspective view of a slip-form table system 100 which is ready to cast, showing reinforcing steel 400, standard lift inserts 420.

Casting

Casting of the slip-form is straight forward. After dimensions and the consistent tightness of the slip-form assembly to the faces of all master blocks has been confirmed one last time, the concrete is placed, vibrated, screeded and troweled in the conventional manner.

Master Block Removal

Once the slip-form concrete has undergone initial curing—after about 24 hours for a typical self-compacting mix—the master blocks can be removed to reveal the void 3000 which will form the precision structural blocks as illustrated in FIG. 19.

Monolithic Master

As previously noted, the first slip-form of its type may be immediately used to produce a monolithic master. This facilitates the layout of future slip-forms for identical parts without ever having to repeat the precision layout and binding of master blocks to build a master; the avoided work can be time-consuming and tedious, and unnecessarily repeating that work introduces a new opportunity for errors to occur. The monolithic master is reinforced as required and provided with standard lift inserts for handling, and it can serve as the template for the production of an unlimited number of consistent slip-forms.

It should be noted that a more portable version of a dimensionally precise master can be obtained using the same methods described herein, but using a precision-cut set of steel plates that are tabbed together and joined to build a full-size master in substitution for the concrete master blocks and monolithic master described herein. A plate steel master can serve all of the same functions as its concrete counterpart, but can be disassembled to create a lighter weight and more compact package to transport.

Lift Master

It should be noted that the first prototype of this concept incorporated a stationary master and a slip-form that moved vertically. This works well for a simple part, but this method would quickly become unwieldy for a complex part with interior voids. This is because each slip-form component would need to be moved independently but uniformly, with lift and alignment mechanisms necessary at several points within the body of the block, and vertical alignment between portions of the slip-form would be subject to change with every movement of the form. One constant in this problem is the fact that the manufactured block is always monolithic. The concept of the lift master takes advantage of this fact to yield an easily operable slip-form table that requires minimal alignment effort. Because the manufactured block 3100 is always monolithic, it should always be possible to support that block, or the base master slab upon which it is cast, with a simple set of lift beams 3200 as illustrated in FIG. 20. In the case of a multi-stack, bottom harvest version of the slip form as described below, the lift master may comprise a stack of blocks that were recently cast in the same form and lowered one block thickness per casting cycle. Such a stack would generally be supported from the floor below. In the case of the simpler and less expensive to build single-block slip form table of this example, the lift master incorporates lift beams that are hung from the slip form table.

If the lift beams extend beyond the edge of the base master and below the stationary slip-form, the two match-cast components can be moved vertically relative to one another by applying tension or compression, depending on the desired direction of movement, between the two. The lift master is then just a monolithic master cast integrally with the necessary number and layout of lift beams.

FIG. 21 is a top perspective view of lift beams 3200 interspersed within an array of casting beams 3300 to form a casting bed 3400. The casting beams offer flexibility in that a lift beam can be placed anywhere within the array, so that a variety of lift beam configurations can be produced out of a single casting bed. In a slip form production environment, the casting beams could logically be replaced with slabs that are built with gaps and slip interfaces to receive lift beams of consistent location, as required for the production of multiple identical lift masters for a specific block geometry.

Lift beams

Lift beams are laid out as required to limit the anticipated lifting forces at each lift point and to limit stresses on the monolithic master and cast block during casting and operation. FIG. 22 is a top perspective view of lift beams 3200 showing plinths 3210 and rebar hoops 3220. The construction of each lift beam incorporates one or more plinths with rebar hoops that extend from the top of each plinth and into the secondary casting of the base master. Lift beams are reinforced as required for structural purposes, and each lift beam is cast with a biaxial sleeve 3230 at each end. The referenced LadderBlock patent application defines a biaxial sleeve as a welded pair of steel pipes that provide perpendicular sleeves through the concrete part into which they are cast. In this case the biaxial sleeve presents first, a vertical sleeve 3232 that aligns with a corresponding vertical sleeve in the slip-form at each lift point (i.e. at each end of each lift beam) and second, a horizontal sleeve 3234 for connection of the drive assembly bottom bracket as described below. The lift beam shown in this example has a 12″ wide by 12″ tall cross-section, with 10″ square by 6″ tall plinths.

Casting Beams

The ideal configuration of a lift master is that of an 8″ thick base master cast integrally with its lift beams, but with a space of about 6″ clear between the top of the lift beams and the bottom of the base master. This clear space is the reason for the plinths on the lift beams. When the 8″ base master is cast onto the lift beam plinths, the top of the base master combines with the plinth height in this case to provide a 14″ depth from the top of the base master to the top of the lift beam. When the lift beam is fully elevated as a part of the slip-form table, this puts the top of the base master at about 2″ above the top of the 12″ thick slip-form. Elevating this casting surface above the top of the slip-form allows the cast block to be harvested without risking damage to the slip assembly, and it exposes the casting surface for cleaning prior to casting the subsequent block.

FIG. 40 shows one example for the detailed steps for fabricating the slip form table components of FIG. 39. The steps comprise preparing the slip form at step 5020, preparing a casting bed with lift beams at step 5040; placing the slip-form on top of the casting bed at step 5060; placing blockouts and reinforcement slip at step 5080; casting the slip form table at step 5100; installing grouted studs at step 5120; fabricating table legs and tie downs at step 5140; and providing a drive mechanism at step 5160.

Step 5020, Prepare Slit Form.

In this example, the slip form is prepared from master blocks as described above.

Step 5040, Prepare Casting Bed with Lift Beams at Desired Locations

The example 6″ clear space may be achieved as follows: a series of 12″ wide×14″ deep simple casting beams are produced and laid out in a series. FIG. 23 is a top perspective view of an example of lift beams 3200 interspersed at desired locations within an array of casting beams 3300 to form a casting bed 3400. Pairs of casting beams either side of each desired lift beam are each built with a slip-form assembly that abuts the lift beam. The tops of the 12″ deep lift beams fall 2″ below the tops of the 14″ deep casting beams. The casting and lift beam array is now ready to receive the slip-form, which will in turn act as the form for casting of the base master. An array of casting beams offers flexibility in the layout of lift beams for a variety of block geometries, but where multiple slip forms of a given geometry are to be built the array of casting beams may be replaced with fixed-width slabs that offer slip interfaces at each side of each lift beam.

Step 5060, Place and Prepare Slip-Form

FIG. 24 is a top perspective view of a previously cast slip-form 210 laid into position on top of the casting bed of FIG. 23, such that the plinths and rebar hoops extend into the slip-form void.

FIG. 25 is a top perspective view of the slip-form casting bed of FIG. 24 with packable material 3410 filling the voids within the slip-for. Sand or other suitable packable material is laid, dampened, and packed into place to fill all voids within the slip-form that are below the tops of the lift beam plinths. This equates to a 4″ layer of sand above each casting beam and a 6″ layer of sand above each lift beam. The compacted sand reserves the desired clear space while providing a suitable casting surface for the concrete that will form the base master; the sand is easily removed after casting and stripping and can be reused.

Step 5080, Place Blockouts and Reinforcement

With the compacted sand in place, the next step in preparing to cast the base master is installing the blockouts and reinforcement. FIG. 26 is a top perspective view of the slip-form and casting bed of FIG. blockouts 3420 and reinforcement 3440 installed. In this example short sections of 4″ diameter post-tensioning duct are used to form block-outs in the base master at each stud location. Stud installation is critical, because it is on these studs that the biaxial sleeves of each manufactured block will be installed prior to casting. It is essential that each stud be vertical and that it be located with precision. One solution that offers the necessary precision is to form oversized block-outs in the base master when it is cast, so that studs can be grouted into position accurately, after the fact and apart from the concreting operation. It is possible to cast these studs directly, but the forces exerted by the concrete during casting can be large enough to displace any elements that are not rigidly held in place. In either case, the studs or the blockouts are also valuable in helping to chair the reinforcing steel cage that is necessary to resist structural actions on the base master. Prior to casting, all blockouts are filled with packed damp sand or other suitable material. The sand prevents concrete from entering the blockout during casting, and is easily removed after the base master has completed initial curing.

Step 5100, Casting

Casting of the base master then proceeds as with any other concreting operation, although special attention should be paid to the finish of the top surface. It is the same finish that will be transferred directly to the myriad blocks that will ultimately be cast on top of it. It should be noted that the method of casting a lift master that incorporates previously cast lift beams has potential value beyond that brought to slip form production. The resulting lift master is, in essence, a beam-stiffened concrete structure. The base master could as easily be a flat wall panel or other structural element that is stiffened by beams similar to the lift beams.

Step 5120 installing grouted studs

FIG. 27 is a top perspective view of a cast base master 380 with lift beams 390. After the base master has cured sufficiently for handling, the slip-form can be lifted to expose the completed lift master assembly where the precast lift beams are monolithic with the newly cast base master.

FIG. 28 is a top perspective view of the cast base master 380 of FIG. 27 with grouted studs installed. After sand has been removed from the clear space between the base master and lift beams and from each grouted stud blockout, the grouted studs can be installed. The mechanism that holds studs in position while it is being grouted can take a number of forms, as long as the studs are held plumb and in the desired position. With the grouted studs rigidly held in the desired position and the bottoms of blockouts plugged to prevent grout leakage, the interstitial space between the stud and the blockout is ready to be grouted. The steel pipe stud 3480 itself may also be grout-filled to stiffen it and to prevent it from catching water or concrete paste during block manufacture. With the completion of grouted stud installation, the construction of the lift master is complete.

Step 5140, Fabricate Table Legs and Tie Downs

Each slip-form component of the example is supported by and tied down to a properly engineered underlying slab (either on-grade or suspended). Slip-forms components can be supported and stabilized by a variety of support means, but the example embodiment is supported by an arrangement of precast table legs, and the table structure gains overall stability by means of tie-downs to the underlying slab as shown in FIG. 4. By virtue of the combination of tie-downs and table legs arranged for stability, a slip-form table is able to resist the moderate lateral forces, gravity loads, and uplift forces that might be encountered during operation.

Production of table legs is simple. Each leg 3500 is cast with two full-height vertical pipe sleeves 3520 that will ultimately align with a pair of corresponding sleeves in the slip-form. The sleeve pairs are positioned using the same center-to-center spacing as the matching sleeves in the slip form. The table legs can be cast on their sides in much the same manner as master blocks, with the pipe sleeves serving as thru-bolted spacers between a pair of steel channels. Using this method, several table legs can be produced in a single casting between a pair of steel channels 3530 and 3532 as shown in FIG. 29.

Tie-downs 3540 may take a number of forms. In this example the tie-downs take the form of a threaded rod 3560, such as course thread post-tensioning bars, that is welded to a base plate 3580. The base plate incorporates two holes for anchor bolts such as wedge anchors that can be drilled and installed to connect the assembly to the underlying slab.

Step 5160, Provide Drive Mechanism

As mentioned previously, the drive mechanism may take a number of forms. In this example, a threaded rod drive is used to induce the required motion. FIG. 30 is a top perspective view of a simple and relatively inexpensive drive mechanism 3700 comprising a drive rod 3710, a drive housing 3720, and a bottom bracket 3740.

Drive Rod

The drive rod 3710 might be of a number of styles of threaded rod, or it could be a solid rod with threaded ends. In this example, a ¾″ diameter “Acme” threaded rod was used. The bottom of the rod passes through a welded nut on the bottom bracket, and the top of the rod receives an inner drive nut pair that is bound to the drive rod by a slot weld between the nuts. The drive nut pair is coupled with standard washers inside of the welded drive housing, which also incorporates a seal and a grease port to allow the housing to be pumped full of grease. The top of the rod may receive a welded top drive nut, or a gear, sprocket, or other drive assembly. In the embodiment presented here, a welded nut is provided below a vertical extension of the threaded rod that can accommodate a variety of drive systems. A nut pair with a washer pinched between the locked nuts is then installed at the top of this extension, and this assembly serves to protect the upper threads and to offer a sacrificial drive nut. If the sacrificial nut gets damaged or begins to round, it can be removed and replaced. While the embodiment presented utilizes standard, inexpensive washers, easier operation can be obtained by incorporating thrust bearings or other features to reduce friction during operation.

Bottom Bracket

The bottom bracket 3740 in this example comprises a steel channel 3741 with its flanges turned down and its web drawn tight against the bottom of the end of a lift beam by a pair of threaded rods 3742 and 3743 that pass through holes in a clamp pipe as illustrated in FIG. 31. The clamp pipe 3747 passes through a horizontal steel pipe sleeve that was cast into the end of the lift beam 390 as shown in FIG. 30.

Alternatively, the bottom bracket could be anchor bolted directly to the underside of the lift beam in a manner similar to that of the drive housing connection, but such anchors would be inaccessible once the table is assembled. The described detail is therefore preferred. On the underside of the web of the bottom bracket, centered on a hole that will receive the drive rod, a standard nut 3744 is welded. It is the turning of the drive rod threads through this nut that will raise or lower the end of each lift beam. When the rod is turned clockwise, the bottom bracket is pulled harder against the underside of the lift beam and the lift beam raises in response. When turned counterclockwise, the bottom bracket is pushed downward, and the threaded rods and clamp pipe drag the lift beam down with it.

Drive Housing

The drive housing might be detailed in a variety of ways. In this example, FIG. 32 is a top perspective view of a drive housing 3720. The drive housing comprises a steel channel 3722 with upturned flanges and holes drilled through its web, and a steel plate 3724 with a centered hole and a short section of steel pipe welded to the plate. The steel pipe is drilled to receive a grease fitting that is tapped into its side, and could be welded to the channel rather than the plate. The unwelded end of the steel pipe grease cup receives a compressible or cure-formed seal to contain grease in the cup. Holes centered in the channel and the top plate each receive the drive rod, such that the welded inner drive nuts and washers on the drive rod get sandwiched between the channel below and the plate above, inside of the sealed grease cup. The top plate is then welded to the flanges of the channel, and the top drive nut and sacrificial nuts are installed. Two outer holes on the drive housing channels receive connectors to the slip form, in this case wedge anchors that are set in holes drilled in the top of the concrete slip form. When the drive rod is turned with a wrench or other mechanical means via the top drive nut, the top of the rod remains stationary as the inner drive nuts are bound within the drive housing. The bottom of the rod passes through the bottom bracket, and as the drive rod is turned the attached lift beam end translates up or down the threaded rod, depending on the direction of rotation. Clockwise rotation of the drive rod raises the lift master by using the bottom face of the inner drive nut pair and washer to pull the channel tighter against the top face of the slip form. Counterclockwise rotation lowers the lift master by pushing the top face of the inner drive nut pair against the underside of the drive housing top plate across a washer, thereby putting the drive rod in compression. Turning in this direction is much easier since the weight of the lift master is also pushing downward, but the control over motion that the threaded rods offer is valuable in achieving the necessary levelness in raising and lowering of the lift master.

Detailed Description of Embodiment—Slip-Form Table Assembly

With all of the necessary components fabricated, the assembly of a slip-form table is relatively simple. On a base slab 110 shown in FIG. 4 that could be cast on-grade or suspended, table legs are laid out and tie-downs installed prior to positioning the lift master on the slab. The slip form is then installed and locked down, and lift mechanisms are installed at each lift point. The slip form table is then ready for use.

FIG. 41 shows one example for the detailed steps in assembling the slip form table of FIG. 39. The steps comprise laying out table legs and tie downs at step 5520; placing the lift master at step 5540; installing the slip form a match-cast base master at step 5560; and installing the lift mechanism and making an initial lift at step 5580.

Step 5520, Layout Table Legs and Tie Downs

Legs and tie downs are one example of a table support means. Layout of the table legs as shown in FIG. 4 is simple. A time-saving step is to temporarily set the slip form on the slab and mark the location of each vertical sleeve in the slip form—the table legs, tie downs, and lift points—directly on the slab, and by concurrently marking the perimeter of the slip form by tracing its outer edge onto the slab such as with a felt-tip construction marker. Marking the sleeve locations can be accomplished by spraying paint down each sleeve to leave a paint mark on the slab, or by another means. Once marked, the layout of the table legs and tie-downs is simple. Each offers some degree of forgiveness, so the layout need not be overly precise. Pipe sleeves in the table legs and the slip form are intended to align, but alignment can be somewhat rough because the connector is a simple length of rebar that fits loosely in the larger diameter pipe sleeve, this offers ample fit-up tolerance. Tie downs are intended to be vertical, but a slight offset in alignment would not be detrimental, so they too offer a comfortable tolerance during fit-up and assembly.

The installation of each tie-down only requires the setting of a pair of anchor bolts. In this example, wedge anchors are set in holes drilled in the slab. In the case of a suspended slab, the tie-downs might instead pass through the slab and be secured with a nut and washer at the underside of the slab. Once the tie-downs are installed and the table legs positioned, the lift master is ready to be set in position.

Step 5540 Place Lift Master

The lift master is positioned prior to installing the slip form. FIG. 33 is a top perspective view of a lift master 400 positioned on the slab 110 on wooden blocks (not shown). The lift master must be properly positioned relative to table legs and to the slip form perimeter lines marked on the slab.

Step 5560, Install Slip Form

With table legs, tie-downs, and the lift master in place, the slip form is ready to be installed. The first means of alignment is provided by simultaneously inserting the tops of all tie-down rods into the bottoms of corresponding sleeves in the slip-form. As the slip-form is lowered further, it must be guided onto the base master 380. This can be accomplished by holding the slip form at an angle as the lower, leading edge of the slip form is lowered into union with the corresponding edge of the base master. The slip form is then slowly lowered and laid flat as the remainder of surfaces mate up between it and the base master. The slip form is then lowered further until it is supported on the precast table legs, and loose rebar dowels are dropped into each sleeve that aligns with a table leg sleeve. These dowels prevent the leg from potentially being kicked out from under the slip form. In this case, a plywood shim was placed on the top of each table leg to provide some cushioning against slight variations in the levelness of the supporting slab. Once the slip form is resting on the table legs and mated with the lift master, washers and nuts are installed and tightened on each tie-down. Tightening these nuts effectively post-tensions the slip form down to the slab, with the table legs acting as separating struts.

Step 5580, Lift Mechanism Installation and Initial Lift

The last step in preparing the slip-form table for use is the installation and greasing of the lift mechanism as shown in FIG. 30. A bottom bracket is installed at the end of each lift beam, and drive rods are lowered through aligned holes in the slip form and lift beam and then threaded into the welded nut on each corresponding bottom bracket. At this point, the drive rod and drive bracket are one assembly. The drive rod is driven down until the drive bracket rests on top of the slip form, then installation is completed by installing the drive bracket anchor bolts and greasing the system. This includes pumping grease into the drive bracket grease cup to lubricate the paired drive nuts, and by filling the vertical sleeve in each lift beam to grease the threaded drive rod above its passage through the bottom bracket. Once all lift points have been fitted with lift mechanisms and greased, the lift master can be run up for the first time. Fully elevated, the top casting surface of the base master ends up at about two inches above the top of the slip form.

Detailed Description of Embodiment—Operation

Once it is fully assembled and operational, the slip-form table is ready to begin producing blocks. Because of the ease of operation, dimensional controls, and rebar positioning offered by this system, high precision blocks can be produced with relative speed by unskilled labor. Workers can be trained quickly and immediately become productive.

FIG. 42 shows one example for the detailed steps in operating the slip form table of FIG. 39 to produce cast parts. The steps comprise installing biaxial sleeves and reinforcement at step 5720; lowering the lift master at step 5740; applying a debonding agent at step 5760; casting concrete at step 5780; curing concrete until lifting strength is achieved at step 5800; raising the lift master and harvesting a newly cast block at step 5820; and cleaning and repeating the casting operation at step 5840.

Step 5720, Installing Biaxial Sleeves and Reinforcement

At this step, the biaxial sleeves are installed onto each grouted stud. FIG. 34 is a top perspective view of biaxial sleeves 3230 installed on the grouted studs 3460 of the lift master.

The biaxial sleeves assist in positioning the reinforcing steel. FIG. 35 is a top perspective view of reinforcement 3440 tied to the biaxial sleeves of FIG. 34. Tying the cage is much easier with the lift master elevated than it would be if the reinforcement cage had to be tied in its final position inside the slip form. Free access to the cage replaces what would have been a cramped operation with limited hand access, as is more common of conventional construction.

Step 5740, Lower Lift Master

Once the reinforcing steel cage has been tied, the lift master 400 and the reinforcement cage it carries is lowered into the slip form as shown in FIG. 36. In this case a total of 10″ of movement lowers the casting surface of the base master to 8″ below the top of the slip form, as required to cast an 8″ thick block. The lift master is lowered uniformly to avoid binding it in the slip form.

Step 5760, Apply Debonding Agent

Before casting concrete, all casting surfaces and any other surfaces of the slip form table that might be exposed to fresh concrete are treated with a debonding agent. Once the debonding agent has been afforded its brief curing time, the slip-form table is ready to receive the concrete that will cast its first block.

Step 5780, Cast Concrete

Once again, a self-compacting concrete mix is utilized in this example because of the quality of formed faces and high early strengths offered by such a mix. Otherwise, concrete placement, vibration, screeding, troweling, and curing operations proceed as with conventional construction.

Of these tasks, the troweling of the finished surface is the most labor intensive. One option to troweling that exists in the industry is the use of concrete stamping techniques to press a pattern into the top surface of freshly cast concrete. A flat surface could also be pressed into the top surface of freshly cast concrete and produce a finish of acceptable quality if the operation ensures that air bubbles will not become entrapped below the stamping surface. This can be accomplished by using a series of small plates with small edge gaps that allow air to escape, or by using perforated plate. Utilizing such a top form would reduce troweling to cleaning up the locations that were not pressed, such as the air escape routes. To obtain a quality finish, though, it would be necessary to press the top form into the concrete with some force. Another advantage of the slip-form table design lies in the fact that it can also be utilized as a concrete press. If, after casting and screeding the concrete to fill the form, the lift master were immediately dropped slightly, a top form could be bolted down to the top of the slip form. Raising the lift master using the drive assemblies would then press the concrete upward against the top form to achieve the desired pressed finish, this might be a series of flat plates or an architectural pattern of any design. A matching form liner could be laid into the base of the form atop the base master to complement the stamped top pattern.

Step 5800, Cure Concrete Until Lifting Strength is Achieved

Once a block is cast, it must be protected from rapid drying and remain undisturbed until it has gained the strength needed for the block to be lifted without damage.

Step 5820, Raise Lift Master and Harvest Newly Cast Block

FIG. 37 is a top perspective view of a cast block 102 from the slip table of FIGS. 23 to 35. Prior to harvesting the newly cast block, it is elevated above the top of the slip form table using the drive mechanisms to uniformly raise the lift master on which it was cast. It is then rigged to a lifting device of suitable capacity through selected biaxial sleeves that are integral to the block. This first lifting may be the most critical loading that the structural block will ever see, considering the fact that the concrete will continue to gain strength rapidly over the next weeks. Blocks are therefore harvested using multiple lift points to minimize concentrated forces, and are immediately set onto a curing stack that uses a mist of water or other means to optimize the strength gain of the concrete.

Step 5840, Clean and Repeat Casting Operation

Once a newly cast block has been harvested from the slip form, the table is immediately cleaned of concrete residue and prepared for the cycle to begin again with the installation of the next set of biaxial sleeves and reinforcement of step 5720.

Detailed Description of Embodiment—Other Embodiments

The slip-form table described herein is a powerful tool that was designed to work reliably and efficiently in solving the problem of producing LadderBlock parts. But like many powerful tools, it has utility that reaches far beyond the originally intended use. This machine can be set up to cast on a shorter cycle by converting it to a multi-stack slip form, and variations of the slip-form can produce concrete shell elements, entire structures, or miniature components. It has also been noted that the table is itself is an operable reinforced concrete structure. A structure of this design could be incorporated into a building design to offer operability that cannot be found in conventional construction.

Multi-Stack Slip-Form

The slip-form table offers the advantage of a comfortable work height above the floor for rebar placement, debonding, concrete placement, troweling, and harvesting operations. A significant limitation of this system lies in the necessity to leave a newly cast block in the form table until it reaches lifting strength; although this can be 24 hours or less after casting using a typical self-compacting concrete mix design. The cost-effectiveness with which blocks can be produced could improve dramatically if the form tables could produce blocks on a shorter cycle than 24 hours. The effects of this limitation can be minimized by the use of high-early strength cements and methods such as steam curing, but these each represent additional manufacturing costs. Another powerful way to accomplish a rapid casting cycle is to cast multiple blocks in a stack, so that a given block can continue to cure while subsequent blocks are being cast. This can be accomplished with minor modifications to the system already described.

Within the limitations of the load capacity of the lift mechanisms, the slip-form table presented herein can be fitted to accept multiple layers of manufactured blocks by lengthening the table legs, tie-downs, and lift mechanism drive rods, and by providing a structured work surface at the appropriate height below the elevated slip-form table, Where the weight of a stack of several blocks exceeds the capacity of a threaded rod drive assembly, another cast block lowering device can be employed to manipulate the blocks. This lowering device can consist of hydraulic rams, air bags, or other mechanical or pressure-assisted devices. FIG. 38 is a top perspective view of a multi-stack slip-form 700 with an elevated slip-form table 710. Note that the studs which are used as the mounting and centering devices for the crosses are generally a part of the lift master in a single-block form table. In a multi-stack form table, the centering studs 750 may be configured to pass through sleeves in the lift master and be secured to the floor below, so the top of the stud remains level with the top of the slip form table.

Cast blocks would then simply be lowered another block thickness below the floor prior to casting a new block. This could potentially be accomplished within 4 to 6 hours after casting with a typical self-compacting concrete mix. The top block in the stack is the first to be lifted and would still require enough time for adequate strength gain, but every block below it could have been cast in a compressed cycle that maximizes the utilization and efficiency of the slip-form table.

FIG. 43 shows one example for the detailed steps in operating a multi-stack version of the slip form table of FIG. 39 to produce cast parts on a shorter casting cycle. At Step 5910, biaxial sleeves and reinforcement are installed. At Step 5920, the lift master is lowered. At Step 5930, a debonding agent is applied. At Step 5940, concrete is cast. At Step 5950, the concrete is cured until a lowering strength is achieved. The strength requirement to simply lower a block in the form is much less demanding than the strength needed to harvest and lift a block. At Step 5960, the lift master is lowered by one block thickness. At Step 5970, the process of Steps 5910 to 5960 is repeated to cast subsequent blocks. At Step 5980, the stack is raised to harvest one or multiple blocks. At Step 5990, the forms are cleaned and the multi-stack casting operation may be repeated.

Yet another improvement that overcomes the limitation imposed by the top block is gained by configuring the slip form table to enable the harvesting of blocks off of the bottom of the stack. Bottom harvest requires that the slip form be supported on cantilevered structure above, that centering stud connections at the ground be simple to release so that studs can be raised, as required to provide clearance for harvested blocks to be moved laterally and out from under the structure. The stack of cast blocks require a dual support system, so that the upper stack is held in place by a temporary support means that might include threaded rods, hydraulic rams, or other devices, while the bottom blocks are lowered and harvested. Movement could be on conveyor rollers, or the blocks could be lowered from the stack directly onto a flatbed trailer. The advantage gained is significant. Because the newly cast block always gets the unstressed cure time of traveling down through the stack, a bottom-harvest multi-stack slip form could be run continuously on a cycle that produces three or four blocks each day; this effectively multiplying the productivity of the slip form by a factor of three or four.

FIG. 44 shows one example for the detailed steps in operating a bottom-harvest, multi-stack version of the slip form table of FIG. 39 to produce cast parts on a shorter casting cycle. At Step 6010, biaxial sleeves and reinforcement are installed. At Step 6020, the lift master is lowered. At Step 6030, a debonding agent is applied. At Step 6040, concrete is cast. At Step 6050, the concrete is cured until a lowering strength is achieved. At Step 6060, the lift master is lowered by one block thickness. At Step 6070, the process of Steps 6010 to 6060 is repeated to cast subsequent blocks. At Step 6080, one or more cast blocks are harvested from the bottom of the stack without interruption to the casting cycle.

Shell Slip-Form

The slip-form table described herein can be thought of as presenting a void, which in this case ranges from 8″ to 24″ wide, that interconnects with other voids to form the shape of a complex structural block that is made of the chords formed in this set of voids. In this case an 8″ thick structural block is cast into the 8″ formed depth of the trough, but other depths can be produced in this slip-form table and in deeper variations of it. These same methods could also be used to produce, instead of thick structural chords, bands of thin concrete shell (1½″ to 2″ or thicker) that could build independently stable folded-plate partition walls, shower enclosures, furniture components, and match-cast segmental structures. Deep components can be match-cast in independent segments, or they can be slip-formed in as many stages as are required to produce the desired depth.

Scale Variations

A forming mechanism such as that described here could be scaled up or down to build an enormous variety of end products. It is conceivable that a multiple-segment slip-form mechanism of this design could be used to slip-form the perimeter walls of a structure such as an above-ground pool, or even to map out the bearing walls of an entire building. Similar methods could also be used to produce miniature parts with complex geometry, including but not limited to scale model LadderBlock parts.

Operable Structures

It has been noted that the slip-form table is an operable structure. It offers true vertical movement between parts that are heavy enough to act independently and not risk being blown away in a strong wind. One possible end use of the match-cast, guided vertical slip, operable structure described herein could be as a concrete structural frame that shares a slip interface with an inner frame, which in turn carries a high roof. Elevating the inner frame a foot or two could provide clerestory lighting and screened ventilation to the occupied space below whenever desired. The ability to release heated air and promote ventilation with such a feature could make a building much more energy efficient and its air healthier. The variety of operable structures that may be realized using the methods described herein could include alternative lifting and elevator systems as well as features such as operable roofs and floors. The structural and architectural possibilities that may be afforded by operable concrete structure will enable functions and utility that cannot be found in conventional construction.

Method and apparatus for precision slip-forming of complex precast shapes

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