Patent Publication Number: US-8114324-B2

Title: Apparatus and method for pressing an outer wall of pipe

Description:
TECHNICAL FIELD 
     The present invention relates to manufacturing three-wall corrugated pipe walls, and more particularly, to an apparatus and method for pressing an outer wall of pipe after the outer wall is extruded onto a dual-wall corrugated pipe. 
     BACKGROUND 
     Drainage pipe has long been used for transporting water in various agricultural, residential, civil engineering, and other construction applications. For example, drainage pipe has been used to create storm sewer systems configured to collect and dispose of water “run-off.” Traditionally, drainage pipe was made from clay or concrete, which caused the pipe to be heavy, expensive, and brittle. In order to improve the ease-of-installation, cost-effectiveness, and durability of drainage pipes, pipes are now often manufactured from alternative materials, including various polymers and polymer blends. 
     One method of manufacturing polymer pipe involves forming a polymer pipe and then extruding an outer layer of polymer onto the outside of the polymer pipe. As a result, the outer layer of polymer constitutes an outer pipe wall that is fused to the exterior surface of the polymer pipe. This outer layer of polymer is generally extruded at a temperature sufficiently high to allow it to bond with the exterior surface of the polymer pipe. Specifically, the extruded outer layer of polymer is extruded at a temperature hot enough to at least partially melt the exterior surface of the polymer pipe, such that polymer chains of the exterior surface and the extruded outer wall intersperse and then cool together. This results in the exterior surface and the extruded outer wall being integrally fused or bonded together wherever they contact each other. 
     Even when the outer layer of polymer is extruded at a high temperature, the outer layer can sometimes insufficiently bond or fuse to the exterior surface of the pipe. Specifically, even though a very thin layer of the exterior surface may weld to the newly extruded outer layer, the level of bonding may be too shallow to provide a sufficient weld between the outer layer and the exterior pipe surface. Thus, a high extrusion temperature can sometimes be insufficient for thoroughly bonding an outer layer beyond the immediately exterior surface of a polymer pipe. 
     Accordingly, there is a need for an apparatus and method for pressing an outer wall of pipe to achieve sufficient bonding between an outer layer of polymer and the polymer pipe. 
     SUMMARY 
     It is an object of the present invention to provide such an apparatus and method for pressing an outer wall of pipe. 
     One exemplary embodiment of the present disclosure provides a method of pressing an outer wall of polymer pipe. The method includes extruding a layer of polymer onto a pipe to form an outer wall of pipe; conveying the pipe including the outer wall of pipe through a pressing apparatus having a pressing element configured to rotate about the pipe; and urging the pressing element against an exterior surface of the outer wall as the pressing element rotates about a pipe conveyed through the pressing apparatus. 
     Another exemplary embodiment of the present disclosure provides an apparatus for pressing an outer wall of polymer pipe. The apparatus includes a frame having an annular carriage; and a pressing element configured to rotate about a path defined by the annular carriage; wherein the pressing element is configured to press an outer wall of polymer pipe when the pipe is conveyed through the annular carriage. 
     Yet another exemplary embodiment of the present disclosure provides an apparatus for pressing an outer wall of polymer pipe. The apparatus includes a frame having a bearing; an annular carriage configured to rotate about the bearing; and a pressing element translatably mounted to the annular carriage; wherein the pressing element is configured to press an outer layer of pipe when the pipe is conveyed through the annular carriage. 
     In this respect, before explaining at least one embodiment of the disclosure in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
     The accompanying drawings illustrate certain exemplary embodiments of the disclosure, and together with the description, serve to explain the principles of the invention. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, to recognize that the claims should be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary embodiment of a press rolling apparatus for pressing an outer wall of pipe; 
         FIG. 2  is a side view of the exemplary press rolling apparatus depicted in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a portion of the exemplary press rolling apparatus depicted in  FIGS. 1 and 2 ; and 
         FIG. 4  is a cross-sectional view of an exemplary three-wall polymer pipe and a portion of the exemplary press rolling apparatus depicted in  FIGS. 1-3 . 
     
    
    
     DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to the exemplary embodiments described above and illustrated in the accompanying drawings. 
     During the manufacture of multi-wall polymer pipe, concentric tubes of polymer may be continuously extruded from one or more extrusion dies. A corrugator may be used to form corrugations into one or more of the layers of polymer as they continuously translate away from the extrusion dies. In one embodiment, a corrugator may be used to form dual-wall pipe having a smooth inner wall and a corrugated wall. The corrugated wall may have a plurality of alternating corrugation crests and corrugation valleys, with the corrugation valleys being fused to the smooth inner wall. In order to improve the performance of such a pipe, it may be desirable to extrude an additional layer of polymer onto the pipe. For example, a cross-head die may be used to extrude an outer layer of polymer onto the exterior surface of the corrugated wall, thereby forming three-wall, corrugated polymer pipe. 
     The outer layer of polymer may be extruded at a temperature high enough to at least partially bond or fuse the outer layer of polymer to corrugation crests of the corrugated wall. For example, the hot outer layer of polymer may at least partially melt the corrugation crests of the corrugated wall. Alternatively, the corrugation crests of the corrugated wall may be heated by use of a separate heating element, in order to increase their level of bonding with the extruded outer layer. However, a high extrusion temperature can sometimes be insufficient for thoroughly bonding an outer layer beyond the immediately exterior surface of a polymer pipe. For this reason, pressure may be applied to the outer layer to increase the depth of bonding beyond the immediately exterior surface of the polymer pipe. Thus, in some cases, it may be desirable to press an outer layer of polymer pipe against the exterior surface of a dual-wall corrugated polymer pipe after the outer layer of polymer is extruded onto the dual-wall corrugated polymer pipe. 
       FIG. 1  illustrates an exemplary embodiment of a press rolling apparatus  10 . Press rolling apparatus  10  may include a frame  12  having a plurality of bearings  14  disposed thereon. In one embodiment, frame  12  may have four bearings  14 , each of the four bearings  14  being rotatably disposed on a quadrant of frame  12 . Press rolling apparatus  10  may further include an annular carriage  16 . Annular carriage  16  may be rotatably disposed on and engaged with bearings  14 . Thus, annular carriage  16  may be configured to rotate about a central axis, relative to frame  12 , as guided by bearings  14 . 
     Press rolling apparatus  10  may further include a drive belt  18 , a pulley system  20 , and a motor  22 . Drive belt  18  may be configured to be wrapped around an outer groove disposed in annular carriage  16  and around wheels of pulley system  20 . At least one wheel of pulley system  20  may be driven by motor  22 . Thus, motor  22  may be configured to selectively control a rotation of annular carriage  16  by manipulating drive belt  18  via pulley system  20 . Annular carriage  16  may be selectively rotated by any other suitable mechanism, such as a rack and pinion drive, a spiral gear, a gas spring, a crank system, a hydraulic system, a pneumatic system, and/or an electromagnetic drive. 
     Press rolling apparatus  10  may further include a plurality of press rolling mechanisms  24  disposed on annular carriage  16 . As illustrated in the embodiment of  FIG. 1 , press rolling apparatus  10  may include two press rolling mechanisms  24 , each being disposed 180° apart from each other on annular carriage  16 . Alternatively, press rolling apparatus  10  may include any number of press rolling mechanisms  24 , as desired. As will be described in greater detail below, each press rolling mechanism  24  may be provided with a pressing element configured to press against an outer wall of pipe as the pipe is conveyed through press rolling apparatus  10 . Even though press rolling apparatus  10  will be described with respect to an embodiment in which press rolling mechanisms  24  are attached to a rotating annular carriage  16 , any equivalent or similar mechanism may be used. For example, annular carriage  16  may be fixed to frame  12 , and a pressing element may be configured to advance around a circumferential path of annular carriage  16  in any way that suitably rotates the pressing element about a pipe conveyed through press rolling apparatus  10 . 
       FIG. 2  illustrates a side view of an exemplary embodiment of press rolling apparatus  10 . As described above, press rolling apparatus  10  may include frame  12  having bearings  14 . Annular carriage  16  may be rotatably disposed on bearings  14 . Motor  22  and pulley system  20  may be configured to rotate annular carriage  16  on bearings  14 . Annular carriage  16  may rotate about a central axis “D”, along which a pipe may be continuously conveyed through press rolling apparatus  10 . In the exemplary embodiment of  FIG. 2 , two press rolling mechanisms  24  are illustrated as being disposed 180° apart from each other on annular carriage  16 . 
     In one embodiment, each press rolling mechanism  24  may include a linkage  26 , a bracket  28 , and a pressing element  30 . Linkage  26  may translatably mount bracket  28  to annular carriage  16 . Bracket  28  may rotatably mount pressing element  30  to linkage  26 . It will be appreciated that any equivalent or similar system of brackets and linkages may be used to allow pressing element  30  to translate and/or rotate relative to annular carriage  16  and/or frame  12  of press rolling apparatus  10 , as desired. 
       FIG. 3  illustrates a cross-section of one exemplary embodiment of a press rolling mechanism  24 . Press rolling mechanism  24  may include a translating member  32 , a bracket  28 , and a pressing element  30 . Translating member  32 , bracket  28 , and pressing element  30  may be fixed to each other in series, as shown in  FIG. 3 , and configured to translate together along an axis “A” through a block  36  mounted to annular carriage  16 . Translating member  32  may include an angled plate  34  disposed integrally therein. Press rolling mechanism  24  may also include a plurality of opposing cam followers  40  configured to engage opposing faces of angled plate  34 . Each cam follower  40  may be rotatably disposed at an end of a cylinder  44  connected to a threaded rod  46 . Cam follower  40 , cylinder  44 , and threaded rod  46  may be configured to translate together in a bore  37  formed in block  36 . A compression spring  42  may be disposed around threaded rod  46  between cylinder  44  and a threaded bolt  48  disposed in an end cap  38 . Compression spring  42  may be configured to urge cylinder  44 , and therefore cam follower  40  in a direction toward axis “A”. As shown in the exemplary embodiment of  FIG. 3 , a pair of opposing cam followers  40  may be configured to contact and press against opposing faces of angled plate  34 . Given a particular geometry of angled plate  34 , compression springs  42  and cam followers  40  may urge translating member  32 , bracket  28 , and pressing element  30  along axis “A” toward a center point of annular carriage  16 . Thus, pressing element  30  may be urged in a direction towards an axis along which a pipe may be conveyed through annular carriage  16  of press rolling apparatus  10 . An amount of urging provided by compression springs  42  may be adjusted by turning threaded bolts  48  so as to compress or relax compression springs  42 . Any other suitable device may be used to selectively urge pressing element  30  toward a center point of annular carriage  16 . For example, a rack and pinion drive, a spiral gear, a gas spring, a crank system, a hydraulic system, a pneumatic system, and/or an electromagnetic drive may be used to selectively urge pressing member  30  toward a center point of annular carriage  16 . 
       FIG. 4  illustrates an exemplary embodiment of a bracket  28  and a pressing element  30  engaging a three-wall pipe  50 . As illustrated in  FIG. 4 , pressing element  30  may be a relatively cylindrical press roller configured to rotate about a portion of bracket  28 . In one embodiment, pressing element  30  may be a press roller made from a solid slug of Teflon®. Pressing element  30  may have a generally rounded profile configured to rotate about bracket  28  and roll across a surface of multi-wall pipe. As illustrated in  FIG. 4 , pressing element  30  may be a press roller having a substantially hexagonal cross-section. In another embodiment, pressing element  30  may be a press roller having a substantially octagonal cross-section. In yet another embodiment, pressing element  30  may be a press roller having a substantially circular cross-section. In yet another embodiment, pressing element  30  may be a press roller having a substantially rectangular cross-section. In yet another embodiment, pressing element  30  may be a press roller having a substantially square cross-section. 
       FIG. 4  illustrates the exemplary pressing element  30  contacting an outer wall of three-wall pipe  50 . Specifically, pressing element  30  may press against an outer wall of three-wall pipe  50 , thereby urging an outer wall of three-wall pipe  50  against an inner wall of three-wall pipe  50 . It will be appreciated that the inward urging provided by press rolling mechanism  24  to pressing element  30  may be used to compress any two or more layers or walls of a pipe having any number of layers or walls, and any type of geometry. Specifically, as illustrated in  FIG. 4 , pressing element  30  may have any cross-sectional geometry that allows it to accommodate changing diameters along a length of multi-wall pipe. Moreover, pressing element  30  may be especially configured to accommodate changing diameters of pipe due to translation of pressing element  30  as allowed by translating member  32 . Thus, pressing element  30  may be configured to press against a pipe having any desired diameter. However, regardless of any translation of pressing element  30 , a sufficient amount of pressing force may be applied to an outer wall of multi-wall pipe by adjusting compression springs  42 , via threaded bolts  48 . 
     Thus, the presently disclosed press rolling apparatus  10 , press rolling mechanisms  24 , and pressing element  30  may be particularly advantageous for use in a method of pressing against an outer wall of pipe. The method may include extruding a layer of polymer from a cross-head die onto a pipe to form an outer wall of pipe. The method may further include conveying the pipe including the outer wall of pipe through a press rolling apparatus  10  having a pressing element  30  configured to rotate about the pipe. The method may further include mounting pressing element  30  to an annular carriage  16  and rotating annular carriage  16  about the pipe. The method may further include rotatably mounting pressing element  30  on a bracket  28  and urging bracket  28  and pressing element  30  against an exterior surface of the outer wall, via a spring bias, as pressing element  30  rotates about a pipe conveyed through press rolling apparatus  10 . The method may further include rotating annular carriage  16  at a pre-determined velocity based on an outer diameter of the pipe and an axial velocity of the pipe through press rolling apparatus  10 . 
     The presently disclosed apparatus and method may be advantageous in forming a proper bonding, fusion, or welding between adjacent layers of polymer in a multi-wall polymer pipe. Specifically, even when an outer wall of pipe is extruded at a high temperature, the presently disclosed apparatus and method may be used to increase the depth of bonding between the outer wall of pipe and an adjacent wall of a polymer pipe. As a result, a multi-wall pipe made by using the above-described exemplary apparatus and method may benefit from increased strength due to the ability of an outer wall of pipe to support forces on the outside of the pipe and from within the pipe. For example, when an outer wall is extruded onto a dual-wall pipe comprising a smooth inner wall and a corrugated wall, the pressing apparatus and method may allow the outer wall to better support tensile forces transmitted between adjacent corrugations of the corrugated wall. 
     The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.