INTERCREATED PLASTIC CONCRETE PIPE DESCRIPTION This invention relates to mixed concrete and plastic pipe in which the inner and outer walls are coated with plastic. The current state of the art in the concrete pipe industry involves casting using the packer head process, the vibration process or the centrifugal casting process. Commonly, inside the wall of steel pipe boxes would be suspended for reinforcement. The packer head uses a rotating head that moves up through the pipe to, (1) disperse the dripped concrete from the top of the external shape, (2) provide consolidation of the concrete within the pipe wall by means of pressure and, (3) at the termination of one or more steps up and down through the pipe forming the internal diameter. The vibration process uses the internal and external forms and the steel reinforcement is dripped into the annular space between the forms. The concrete is then introduced into the annular space by gravity and subjected to a high frequency vibration to obtain the required compaction and consolidation. The centrifugal casting process uses a horizontal rotating mold with caps inside which the concrete is introduced and the consolidation is achieved through centrifugal force. The finished pipes (in all the processes) are then moved to a curing area and demoulded from the shapes. The forms are then returned to the production station and the process is repeated. Since the finished pipe is demold from all support work immediately after casting, the concrete mixtures used in those processes must be very dry firm mixtures that exhibit zero or negative settlement. Settlement measurement involves using a tapered steel cone filled with the concrete mixture, then the cone is rotated so that the longer radius end of the cone sits on the floor and the radius of the smaller radius end is toward above. The cone is removed and the amount of settlement or fixation of the concrete is measured in relation to the top of the cone. Zero settlement refers to a condition where fixation does not occur. Negative settlement refers to a concrete mix where the water could be added and still have a zero settlement result in the test. Since the pipes must remain without vertical supports, the mixtures used in this process have little flexibility and sometimes the pipes exhibit an inconsistent or poorly consolidated material. In addition, the pipes need to be cured in a humid environment, commonly cured with steam, to allow the finished pipes to have enough moisture to fully hydrate the cement in the mix so that the overall strength of the concrete can be achieved. The limitations of the very dry mix inhibit the industry from taking advantage of many possible mix designs to obtain better consolidation and stronger strengths. In addition, the exposed concrete may change slightly and lose its dimensional tolerances through the drying process. The other limiting characteristic of the processes described above is the need for fixed equipment for each size and wall thickness of the pipeline produced. This equipment is expensive and must be produced for a high demand environment where it is subjected to intense compaction pressures and vibration levels, as well as to the abrasive nature of the dry concrete mix. The pipes produced by this procedure have several problems or limitations. To obtain the three edge support resistors required for the underground deposit and to minimize the amount of steel required, the walls are relatively thick, making the pipes heavy and more difficult to handle and limiting the distance can be transported economically. The first failure mode in the three edge support test is the 0.25 ml (0.01 inch) crack that typically occurs either in the crown or in the lowest part of the pipe. While this is not a structural fault, (it indicates the passage of all tensile stresses for steel reinforcement) it is the common design parameter since many of the users do not want a crack such as this one that allows the water or other corrosive materials corrode the reinforcing steel. This leads to the main limitation in the use of concrete pipes for sanitary drains. In many areas of the country, hydrogen sulfide corrosion of sanitary drains is a severe problem. The alkaline nature of cement paste in concrete is particularly susceptible to the attack of sulfuric acid formed from the generation of hydrogen sulfide in sanitary drains. Hydrogen sulfide is the harmful and lethal gas with the odor of (decomposed blanquillo) that results from the biological breakdown of human and animal waste. To combat this problem, highly plasticized PVC linings were created to be cast inside the internal diameter of concrete pipes. Those linings were designed to provide only corrosion protection, and they have no rigidity and do not offer structural improvement at all. Those linings were successful in providing protection against corrosion;
however, they have other problems. Their extremely flexible nature makes them difficult to handle in the pipe manufacturers' plants and temperature differences were important since those linings had to be placed around the internal shapes of fixed diameter. These linings had a very high coefficient of thermal expansion with respect to steel shapes to depend on the ambient temperature at which they could be adjusted closely or very loosely. The other problem was to protect the joint area between the sections of pipe from a strip of PVC material several centimeters wide that had to be welded by hand into the liner over adjacent pipe sections in the pipe after installation in the countryside. The result of production problems and field welding made in this system is expensive and limits the scale of size for those accessible to the entrance of man. There have been several attempts to use fiberglass as an interior and exterior "lining" for concrete pipe. These products were associated with the centrifugal casting manufacturing process previously described. No manufacturer in this country is currently using this mixed procedure, a manufacturer that has the capacity for emptying by centrifugal force. The limiting factor of this manufacturing process has been that it is very slow and expensive. In the plastic pipe industry there have been some offers of composite product, the closest one to the invention being described here is a product called frame pipe. This is a pipe with a thin internal and external shell connected by networks in a frame configuration that makes an angle between the inner and outer layers. This part of the pipe is created with a vertical extrusion where the networks move longitudinally with the pipe body and the procedure requires a different die for each size. The annular space between the networks is filled with a lightweight cellular concrete mortar for rigidity. This mixed pipe behaves like a flexible pipe, meaning that it flexes progressively and significantly under a load. The lightweight concrete performs as a filler to provide some rigidity to increase the stiffness of the pipe and keep the plastic members in their optimal location. Other mixed plastic products include plastic foam core, metal pipe or tube and fiberglass lining, and resin mortar pipes. The technique described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is "prior art" with respect to this invention, unless specifically designated as such. In addition, this section should not be considered as meaning that a search has been conducted or that other relevant information exists as defined in 37 C.F.R. ยง 156 (a). The invention provides concrete pipe of any desired diameter and thickness as a combination with internal and external plastic coating. Plastic coatings create a rigid pipeline with advantages over concrete alone. The pipe is defined by plastic profiles with spirally wound ribs that interlocked to form the internal and external walls of the eventual pipe. The annular space between them is filled with concrete and vibrated to fill any gaps. BRIEF DESCRIPTION OF THE DRAWINGS A detailed description of the invention is hereinafter worded with specific reference to the drawings in which: FIGURE 1 is a perspective view of the concrete pipe lined with composite plastic of the invention; FIGURE 2 is an end view of the pipe of FIGURE 1;
FIGURE 3 is a side elevation view of the pipe of FIGURE 1 showing the outer plastic layer wound helically; FIGURE 4 is an enlarged enlargement of FIGURE 2 showing the intertwined inner and outer plastic layer, wound with concrete; FIGURE 5 is an enlarged enlargement of FIGURE 2 showing the ribs that lock inside the concrete; FIGURE 6 is a cross-sectional view through lines 6-6 of FIGURE 2; FIGURE 7 is an end view of a pipe showing that the pipe can be rounded; FIGURE 8 is a simplified mechanical diagram of a pipe forming machine; FIGURE 9 is a top plan view of the machine of FIGURE 8; FIGURE 10 is a simplified mechanical diagram of the machine of FIGURE 8 showing the load of concrete; FIGURE 11 is a top plan view of the machine of FIGURE 9 showing the load of concrete; FIGURE 12 shows a mold clamping mechanism; and FIGURE 13 shows a final treatment of the composite pipe. With reference to FIGURES 1-7, the invention described herein is a pipe with a rigid composite wall 10 using plastic elements 12, 14 and concrete 16 in a design that transmits by levers the best structural aspects of each material. The design offers the best structural performance, reduced weight over existing concrete pipes, corrosion protection and spill removal from external hydrostatic forces. Due to the way in which the plastic and concrete elements are used, the manufacturing process is significantly changed from the existing processes either in the production of plastic pipe or concrete, resulting in the elimination of fixed equipment for each pipe size, the use of steel reinforcement and the need for special healing chambers. The only characteristics of the pipe 10 by itself and the production process will be described below. Pipe The pipe 10 is formed using pipes 12, 14 made from a plastic profile with ribs, wound spirally for both the internal and external diameter, with the ribs 20 extending into the annular space of the pipe. This plastic profile is rigid, ie the tubes 12, 14 formed make a self-supporting pipe in and of themselves. The annular space is filled with concrete 16, vibrated to provide full consolidation and filling of the spaces in and around the ribs 20. This locks the plastic 12, 14 and the concrete 16 together allowing the structural interaction between the two materials. The design places the plastic 12, 14 on the internal and external extremities of the structure, the points where the tensile stresses in the support of three edges or crush tests are higher. This allows the plastic, which has much higher tensile strength compared to concrete, to transport the tensile forces. Concrete, which has a superior modulus of elasticity and compressive strength, provides rigidity and transports compressive stresses. The interaction of the two materials produces superior structural performance without the need for internal steel reinforcement to transport tensile loads. Table 1 below compares the results of the three-edge support tests on the composite pipe and compares with the requirements for both reinforcement pipes and without reinforcement of different wall thicknesses. The test was conducted by Twin City Testing of St. Paul, Minnesota.
NON-REINFORCED CONCRETE PIPE NON-REINFORCED CONCRETE PIPE
PIPELINE COMPOSED OF CONCRETE AND PLASTIC
The values for the support strength of three required edges are taken from ASTM C-14 for concrete pipe without reinforcement and ASTM C-76 for reinforced concrete pipe. Pipe without reinforcement does not have a resistance value of three final edges as it structurally fails once a significant crack is formed. The values required for the reinforced pipe are the same no matter what wall thickness is used, the change is in the steel required to reinforce the pipe. Pipes with thinner walls require more steel reinforcement to obtain the same three edge test support results. By analyzing the tables it can be seen that the composite pipe gets more than twice the performance of the strength test on a comparable wall thickness basis when compared to concrete pipe reinforced with conventional steel. In addition, after the crack of 0.25 mm (0.01 inch) occurs, the pipe with composite walls begins to behave more closely to a flexible pipe, that is, under the increasing load the pipe flexes significantly without structural damage to the inner pipes and external plastic. The internal and external tubes are also saved from cracks, so they are not exposed to corrosive materials. The internal diameter of the plastic is applied to the aforementioned corrosion openings since the type of plastic used in the strip can be varied, the strips can provide protection against corrosion in some industrial applications where the waste streams can vary widely in temperature and the chemical conformation from the typical municipal water currents. Production process . The unique characteristics of the production process are characterized by the flexibility and infinite variability obtained through the elimination of fixed equipment. This flexibility starts with the rolling machine produced by the plastic tubes. The machine is infinitely variable within the range of size that the producer wants to build a machine. This winding machine is protected by patents issued previously for Mr. Stanley Menzel from Australia. The formation of helically wound plastic pipe is described in U.S. Patents 5,074,943; 4,995,929; 4,977,931; 4,687,690; 4,616,495; 4,566,496; 4,435,460; 4,337,564; 4,308,082 and 4,209,043, the descriptions of which are incorporated herein. The present process involves winding a tube 14 with the ribs 20 pointing to the shape of the inner diameter and a tube 12 inward, ie with the ribs 20 pointing to the outer diameter. In this concept of use, an internal "outward" tube combined with the inner diameter tube to constitute a concrete pipe 10 that will eliminate the fixed shape for each size requirement is one of the key features of the process of the invention. Since "the form" becomes part of the pipe 10, it allows the process to be very flexible in the use of different mixing designs to impart certain structural properties, assist in the placement of the concrete in the form, ensure adequate moisture for completely hydrate the cement and allow the pipe to maintain its dimensional tolerances during the cure. A second key element of the invention of the process is that with the shape that becomes part of the pipe and the resulting flexibility in the characteristics of the core material, different techniques for introducing the core material will be allowed. In the aforementioned prototypes, concrete 16 was the core material and the annular spaces between tubes 12, 14 were sufficient to allow the introduction of concrete in a "draining" manner by conventional gravity feed. As the annular space changes and as the need for different materials in the core arises, other filling methods may be used such as vacuum, pumping, injection or some combination thereof. Finally, the containment of the concrete in the structural "form" eliminates the concerns regarding the drying of the concrete too fast and therefore eliminates the need for special healing rooms. It is anticipated that the production of pipe 10 would be processed better as follows. The desired pipe size is determined and the outer plastic layer 12 is formed in a pipe forming station using a helical pipe winding machine as patented by Mr. Menzel, referred to above. The inner pipe 14 is formed in a similar station of a diameter required for the internal dimension of the finished pipe 10. Note that the pipes 12, 14 have the ribs 20 for contacting and joining the concrete. The tubes 12, 14 are wound so that the ribs 20 face the concrete:
With reference to Figures 8-11, the inner and outer plastic tubes 12, 14 are then moved to a casting station 30 which is preferably located below the floor level 32 so that an operator 34 can easily observe filling the ring 36 between the tubes 12, 14. The station 30 includes a central fixed post 40 and spaced peripheral poles 42. A mold holding mechanism 56 having a central hole 58 so that it can pass over the central post 40 it is positioned on top of a vibrating machine 60. The mold clamping mechanism 56 as shown in Figure 12 can be made of steel and defines the lower end of the pipe to be cast. The central post 40 includes a plurality of adjustable guides 44 that can be moved out of said post to define and increase the diameter of the interior of the pipe 10 to be formed. The guides 44 will preferably include arcuate members 46 that closely engage the inner plastic tube 14. A tube 14 is placed on the post 40 and the guides 44 are moved out of contact and hold the tube 14 in position. The outer peripheral posts 42 include a similar adjustable guide 50 with arcuate members 52 to hold the outer plastic tube 12 trapped. Again, it is desirable if the arcuate members 52 define the majority of the circumference of the tube 12 so that the tube is kept clear. movement during concrete loading. It may be desirable to add vacuum to the arcuate members 46, 52 so that the plastic of the tubes 12, 14 is held toward the arched members instead of simply splicing. Figures 8-11 show a concrete feed conveyor 64 that transfers the mixed concrete 16 to a rotary distributor 66 that may be mounted to the center post 40. As best seen in Figure 11, the distributor 66 rotates allowing the concrete is evenly distributed within the ring 36 to form the concrete of the pipe 10. The necessary vibration can be supplied by the underlying vibrator 60. Generally, the concrete 16 itself can be mixed by a high revolution high shear mixer. , a conventional slat mixer or the tray mixer as used in the precast concrete plants, transported to a fixing hopper and dripped into the conveyor 64 where it can be directed into the ring 36 as described. After the concrete fills the ring 36, the pipe 10 is essentially formed. A hoisting cr70 can be moved over the pipe 10 thus formed, attached to lifting lugs 72 on the mold holding mechanism 60 and used to raise the formed pipe 10 to a curing station. The next pipe that is to be formed is made by repeating the process. The simple adjustment of the guides 44, 50 changes the diameter of the pipe to be formed, when used in conjunction with the different sizes of pipe 12, 14. The process of using the pipes 12, 14 for the shapes makes very Easy to sell any pipe size if desired. The thickness of the concrete is fixed by the selection of the tube sizes 12, 14 and the adjustment of the guides 44, 50. After being formed, the pipes 10 may require finishing depending on their intended uses. If the tubing is used in the formation of microtunnels, the ends 82 can be flattened by grinding to avoid tip loading during the cladding. The ends 82 can be coated with concrete epoxies, polyester resin or covered with plastic welded to the inner and outer tubes 12, 14 if a seal is desired. The ends 82 of the pipe 10 can also be treated to prepare the joints between the adjacent pipes. Typically, the outer edges of the pipe ends 82 can be molded approximately 3 inches (7.6 cm) to remove the plastic pipe 12 and some of the concrete 16, typically up to the depth of the ribs 20. A collar 82 of steel, stainless steel or plastic can slide over the ground section in such a way that it extends past the ends 80 and can be used to join with another pipe with its molded end. . Although the drawings show a fully lined composite pipe, it is possible to remove the inner, outer or both layers of plastic 12, 14 so that the formed pipe can be completely lined, lined on the surface or unlined. The benefit is that customary pipe sizes can be formed using the pipes 12, 14 as shapes, whether they remain incorporated in the final pipe or not. Obviously, if a pipe 12 or 14 is not part of the final pipe, it will not include the projection ribs 20 to make contact with the concrete. The outer tubing 12 can be removed simply by heating to expand and release by jumping, or release agents used to decrease adhesion can be used. Furthermore, although the formation of tubes 12, 14 is expected to be by means of a helical winding as in the Menzel patents described, any preformed plastic tubes can be used. Spirally wound plastic tubes are not required, they simply make the process of forming customary pipes easier because they do not need to order preformed plastic pipes.
While the invention can be modalized in many different forms, the specific preferred embodiments of the invention are shown in the drawings and are described in detail herein. The description herein is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. This completes the description of the preferred and alternative embodiments of the invention. Those of skill in the art can recognize that other equivalents of the specific embodiments described herein, the equivalents of which are intended to be encompassed by the claims appended hereto.