MXPA98005786A - Process for manufacturing reticul polyethylene pipe extremes - Google Patents

Abstract

Disclosed is a unitary molded, cross-linked polyethylene tubular connector and a method for forming the connector with various end configurations (eg, molding, widening). The process combines the ease of thermoplastic processing combined with the desirable physical properties of a thermosetting material. The connector is suitable as a replacement for copper pipes with associated fittings as well as for polybutile pipe

Description

ir - 1 - PROCESS FOR MANUFACTURING POLYETHYLENE PIPE EXTREMES RETICULATED TECHNICAL FIELD 5 The invention described herein generally pertains to a method for processing polyethylene pipe ends, for example, widening of at least one end of polymer pipe without compromising wall thickness, so that the work piece is allowed to be suitable for pipe applications or to manufacture at least a cone tip configuration outside the walls of the pipe or to process one or both ends of the pipe using the technology described in this application, or combinations of the same. The reticulate can occur either before the manufacturing process or subsequent to it, based on the integral force required at the ends of the pipe.

BACKGROUND OF THE INVENTION 20 In plumbing installations, copper tubing has been widely used. In risers, used to connect pipes to installations or tanks, the end of the copper pipe is shaped to form a surface of bulb seal and such a bulb includes a flange that allows the pipe and therefore the sealing surface of the bulb to be brought into an incident coupling or sealant with the installation. The cost of such copper tubing and the cost of forming it to allow the connection of such facilities to the tanks is substantial. More recently, polybutylene has been approved for use in plumbing. The pipe or tube made of polybutylene is usually joined by heat fusion, mechanical compression and cold flare techniques. In order to provide such a polybutylene pipe with a bulb sealing surface or an end cap for such purposes, various techniques have been used. Two commonly used techniques are: (1) welding, by rotation of a bulb molded separately on the outer diameter (O.D.) of the end of a bulb; or (2) molding a bulb insert over the O.D. from the end of a tube. All these processes are inconvenient in terms of costs and operation. Most require separate molded parts which must be joined to the pipe in assembly operations. In addition, a two-part pipe end cap or a sealing construction thereof does not have the operating integrity or expected useful life of the pipe itself. In the rotation welding technique, excessive clamping pressures may cause the loaded part to detach or detach from the O.D. of the pipe and the parts interface provides a possibility of leakage. In the case of a neoprene or similar, washers are used in the O.D. of the pipeline, the same susceptibility to leakage at the interface is present. In addition, a flange formed to receive the washer itself can create a point of weakness if excessive clamping pressures are used. In addition, it is known that neoprene washers deteriorate over time and exposure to temperature. Finally, insert molding drives hot material onto a cold tube surface, which can be separated from the tube. The solution to this problem is to provide polybutylene tubing with a united bulb sealing surface of unitary construction as detailed in U.S. Patents 4,316,870, 4,446,084 and 4,525,136, which are hereby incorporated by reference in their entirety. The purpose of these references, however, is to describe the ability to maintain a constant diameter opening within the pipe, while the thickness of the wall is variable. This is necessary, due to the configuration of the mold cavity, and the insertion of the mandrel into the pipe during the processing steps. A corresponding associated problem with the male end formation described before the polybutylene pipe, is the ability to widen the opposite end of the pipe, without any compromise of the thickness of the accompanying wall, which would make the product unsuitable for all pipe applications for which polybutylene has been approved, provided that the wall thickness is maintained at 1.6 mm + 0.3 mm (0.062"+ 0.010"), as defined by ASTM 3309. In particular, it is desirable to use polybutylene tubing with OD 9.5 mm (3/8") with a wall thickness of 1.6 mm (1/16" or 0.062") and then insert a 12.7 mm (1/2") CTS adapter (copper tube size) of OD Nominal diameter of 12.7 mm (0.501"). The only way this can be achieved is through the widening of one end of the pipe from an OD of 9.5 mm (3/8") (6.4 mm ID or internal diameter). 1/4")) to an OD of 15.9 mm (5/8") (12.7 mm (1/2"ID)). Although it is possible to use OD pipe of 15.9 mm (5/8") to start, This uses more untreated materials than necessary. The prior art solutions for the formation of a spreading at one end of the polybutylene pipe is by heating a portion of the end of the pipe, followed by insertion of a mandrel into the heated open end, the O.D. of the mandrel matches the inside diameter (I.D.) objective of the pipe. Although this approach will broaden the pipe, it is unable to reproducibly produce a pipe product with a constant wall thickness of 1.62 mm + 0.3 mm (0.062"+ 0.010") through the flared end, particularly in the narrowing region of the pipe. widened This is due to the fact that the broadening is elaborated by expanding the I.D. and therefore thin the walls. A solution to this problem is found in the pending US patent application Serial No. 08 / 327,028. However, the current trend is the displacement of thermoplastic materials, for example, polypropylene, polybutylene, etc., to thermoset materials, for example, cross-linked polyethylene. However, this displacement in materials is not easy insofar as there are several processing changes which must be incorporated in order to manufacture acceptable parts. Since thermosetting materials can not be extruded like thermoplastics, different processing conditions must be used in different sequences in order to obtain similar functionality for the product. For example, it is not possible to simply take a cross-linked polyethylene tube and mold it into a bulb end by taking the polybutylene technology described in the prior art. The previously crosslinked material will not chemically bond itself even when hot to a transparent state. This means that the material at the formed ends does not seal completely on itself, but rather is molded in place with pressure. A solution of the prior art to this problem is the use of inserts or metal inserts which are placed in the cross-linked polyethylene tubes and subsequently tightened in order to obtain a splice. This is an inherently weak point in the final product, and the industry has long sought to find a solution to the problem of developing a part of a piece pipe made of a thermosetting plastic.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, there is provided a method for processing polymers which will allow a workpiece to have formed / formed ends in one piece from a single piece of pipe. An object of this invention is to provide a process for widening a tube of initial internal diameter to a larger internal diameter while maintaining at least a constant wall thickness through the pipe to produce a thermoset plastic part. Another object of this invention is to provide a process for forming a shaped end of a sealing surface on a thermosetting tube wherein the forming results in a thermally bonded end of constant internal diameter, the part that has been formed from the polybutylene tube and which, in one embodiment of the invention, is crosslinked subsequent to the formation of the manufactured end.

These and other objects of this invention will become apparent when viewed in the light of the drawings, detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may take physical form in certain parts and arrays or arrangements of parts, a preferred embodiment of which will be described in detail in the specification and illustrated in the accompanying drawings which form, part thereof, and in which: Figure 1 is a fragmentary vertical section of the dies used to form the pipe according to the present invention, such dies are shown separated from each other; Figure 2 is a view similar to that of Figure 1 showing the pipe inserted through the female die, partially inserted into the male die in which a predetermined distance is projected from the first; Figure 3 is a view similar to that of Figures 1 and 2 showing the tube projection portion being heated; Figure 4 is a view similar to Figures 1-3 showing the dies that come together; Figure 5 is a view similar to that of Figure 4, showing the closed dies; Figure 6 is a fragmentary elevation of the end of the tube as formed by the process shown in Figures 1-5; Figure 7 is a perspective view showing the male and female segment of a pipe section manufactured in accordance with the teachings of this invention, wherein the male segment is an integrally molded bulb and the sealing surface and the female segment is shows a larger diameter, the thickness of the pipe is constant through it, with a threaded nut internally shown slightly below the male segment, - Figure 8 is an enlarged cross-sectional view taken along the length of the line 8-8 of figure 7; Figure 9 is a perspective view showing the pipe of Figure 7 illustrating a non-linear configuration of the pipe; Figure 10 is an enlarged cross-sectional view, similar to that of Figure 8, illustrating an increased thickness of the pipe in the widened region; Figure 11 is a fragmentary vertical section of the dies used to form the pipe according to the present invention, the dies are shown separated from each other; Figure 12 is a view similar to that of Figure 11 showing the pipe inserted through the female die, and projecting a predetermined length therefrom; Figure 13 is a view similar to that of Figures 11 and 12 showing the tube projection portion being heated; Fig. 14 is a view similar to that of Figs. 11-13 showing the suction die retracted to the portion of tubing projecting backward within the subsequent half-expanding punching die; Figure 15 is a view similar to that of Figures 11-14 showing the joining dies; Figure 16 is a view similar to that of Figures 11-15 showing the closed dies; Figure 17 is a perspective view showing the male and female segment of a pipe section manufactured in accordance with the teachings of this invention, wherein the male segment is a shoulder integrally molded with a soft cone tip sealing surface and the female segment is shown enlarged to a larger diameter, the thickness of the pipe is constant through it, with an internally threaded nut that is shown slightly below the male segment; Figure 18 is an enlarged cross-sectional view of the prior art tubing connector; Fig. 19 is a side view showing a partial cross section showing a pipe connector having a radiated sealing and a conical sealing means, with a stainless steel overtravel; Figure 20 is a fragmentary vertical section of the dies used for the sealing end of the pipe according to the present invention, such dies are shown separated from each other; Figure 21 is a view similar to that of Figure 20, showing the pipe inserted through the female die, partially inserted into the male die and a projection a predetermined distance from the first; Figure 22 is a view similar to that of Figures 20 and 21 showing the projection portion of the tube being heated; Figure 23 is a view similar to that of Figures 20-22 showing the joining dies; and Figure 24 is a view similar to that of Figure 23 showing the closed dies.

DETAILED DESCRIPTION OF THE INVENTION Now with reference to the drawings, wherein the representations are for purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting the same, the figures show lengths of plastic pipe cut-outs on which various configurations have been incorporated. about them. As can be seen in the figures, the pipe comprises a vertically upper fixed mold (10) and a lower mold (11) vertically movable. The upper mold or die (10) includes a central perforation (12) and an ascending tube (13) secured to the upper part thereof having an I.D. equal to I.D. of the perforation (12). The lower surface of the upper mold is provided with a cylindrical projection (14) projecting centrally therefrom. The lower end of the perforation is provided with a conical flared portion (15), the lower end of which is provided with a small radius that is observed with the number (16). Radially beyond such a radius, the perforation ends at an edge (18) extending axially. The lower mold (11) includes a body (20) which can include an annular conduit (21) for circulation of cooling medium therethrough. The body (20) is threadedly connected to the rod (22) of a piston-cylinder assembly and is adjustably fixed thereto by the nut (23). The upper part of the mold or punch (11) is provided with a central recess that is generally shown with the number (25) which includes an upper cylindrical portion (26) in which the axial projection (14) of the upper mold is designed tightly for telescopic coupling. The lower end of the cylindrical portion is provided with a flange (27) that separates the cylindrical portion from the recess of the circular bulb forming a cavity (28a) or a widened cavity (28). The lower circular bulb forming the cavity is provided with an axially circular and horizontally facing end face (29), which is selectively larger in diameter than the diameter of the perforation (12). Projecting axially from the bottom of the recess (25) is a guide rod (30), the upper part of which is provided with a pilot tip or tip portion (31). In Figures 1 and 20, the upper and lower molds or dies have been placed in an intermediate position in relation to one another where the inner mold (11) has been placed in an intermediate raised position and the position can be determined by a stop adjustable retractable as seen with the number (33) in Figure 1. In such a position, the pilot tip of the guide rod (30) projects into the perforation (12) as shown. With reference to Figures 2 and 21, it will be noted that the upper part of the guide tube (13) is provided with a rear stop which is observed with the number (35) which can rotate towards the top of the tube (13) guide for oscillating movement to and from a free position of the ID of such a tube on the I.D. of such tube.

A section of extruded polyolefin plastic tubing, which may or may not be cross-linked at this point in manufacture, cut to a predetermined length, is now inserted downwardly, through the guide tube, as shown in (37) for project from the lower end of the upper mold (10). The dimensions of O.D. and of I.D. of the tube are such that the tube will fit tightly in the I.D. of the perforation (12) with the I.D. of the tube tightly fitting over the O.D. of the rod (30). It is important that the tube (37) projects a predetermined distance below the upper mold (10). This predetermined distance can be obtained in several ways. When the operator inserts the tube, the operator can ensure that the upper part of the tube is in the same plane as the upper part of the guide tube (13) and rotate the stop (35) back on top of the tube calibrating the tube against such top stop. In this way, the length of the tube can be calibrated from the upper end to project at a predetermined indicated distance. Alternatively, a calibration bar, which is shown with the number (40), can be used for contact with the lower end of the tube to obtain the desired projection. With the molds still in their intermediate position and the tube properly positioned, and projecting from the upper mold, the projection end of the tube is now heated as shown in Figure 3. The heating of the tube can be carried out in various ways. In Figure 3, two heating blocks (42) and (43) are used, each provided with electrical heating elements that are observed with the numbers (44) and (45) respectively, to confine the projection end of the tube (37) among them. Of course, it will be appreciated that other forms of heat application may be used such as sonic systems or a heating jacket using oil or other heating means. The projection end of the tube is heated for a predetermined period of time so that the projection end of the tube is heated for a brief period of a complete melt, but long enough to make the material flexible enough to be molded when the dies they join. Although those skilled in the art are familiar with the temperatures described in this operation (e.g., 315-482 ° C (600-900 ° F)), for illustrative purposes only, this temperature will be about 371 ° C ± 14 ° C ( 700 ° F + 25 ° F) for a time of between 10-30 seconds in the case of polypropylene, and approximately 371 ± 14 ° C (700 ± 25 ° F) for a time between 15-35 seconds for cross-linked polyethylene. The key is to balance the temperature and the fusion time inside the heating blocks. It is within the abilities of a person familiar with the art to vary the time and / or temperatures indicated to obtain the desired degree of "softness" necessary for further processing. After the desired amount of heat is applied, the heating blocks are removed. Based on the polymer and / or time and / or temperatures used, a cooling cycle can be used before the start of the next stage. If a lower gauge is used, the gauge (40) is also removed and the retractable step (33) is removed. With the back stop (35) in place, the piston-cylinder assembly of the rod (22) now further extends as seen in Figs. 4 and 23, and the projection end of the tube is housed in the face (29). ) bottom of the cavity (28) that forms the bulb and begins to form, as seen with the number (52). As the lower mold (11) moves upwards as indicated by the arrows (54) and (55) in figures 4 and 5, and in figures 23 and 24, respectively, the axial projection (14) of the upper mold it engages telescopically within the cylindrical recess (26) of the lower mold. The lower mold continues upwards, to the position shown in figures 5 and 24, forming the tube end as indicated. During such movement, the back stop (35) prevents the tube from moving upwards with respect to the upper mold. The piston-cylinder assembly extends completely until the edge (18) of the upper mold engages the flange (27). Such an edge will tend to remove or make easily removable any burrs formed between the surfaces in telescopic coupling of the molds. Alternatively, a stop or gauge ring can be provided, as noted with number (57) to limit the relative movement of the molds to prevent wear on the edge (18). When the molds are completely together, as seen in Figures 5 and 24, a cooling medium can be circulated through the duct (21), as seen in (58). Although water is preferred, it will be appreciated that the cooling medium can be any of many other fluids such as oil or a gas. After the mold has cooled for a predetermined time, the piston-cylinder assembly of the rod (22) is completely retracted and the upper mold can be indexed horizontally so that the tube now formed can be removed. If any flash appears, it can be easily removed from the tube. Although the discussion has focused on a higher mold constituted of a unitary construction, it is equally considered that a split mold can be used. In this embodiment, and when the piston-cylinder assembly is completely retracted, the divided halves of the upper mold (10) will open and the part will be removed from the upper mold, in a vertical direction. After the tube is removed, the upper mold remains in alignment with the lower mold and the stop (33) is returned to its position and the piston-cylinder assembly is extended to put the molds back to the original position shown in FIG. Figures 1 or 20, so that the process can be repeated. It will be appreciated that the illustrated tools may be oriented horizontally or vertically and the recess configurations may be easily altered to form a widened end of varying configurations. In addition, the tube holder (13) can be easily changed to accommodate pre-cut tubes at different lengths. In the practice of the process, however, it is important that the heated end projecting from the tube is substantially adapted to the volume of the matching recess in the two dies or molds. Whether used horizontally or vertically, the relatively fixed mold 10 can be finished to the female mold, while the mold 11 is in motion with the guide rod projecting therefrom and retaining the I.D. The tube can be finished in the male mold or die. The product resulting from the process of Figures 1-5 is seen in Figure 6. The plastic tube formed in this manner includes an integrally formed widened end into which a suitably sized copper splice, for example, can be properly inserted. The plastic tube formed in this manner includes an integrally formed widened surface (60) extending from the end face (61) of the conical neck tube (65). The end face (61) of the tube has an I.D. and O.D. larger compared to the rest of the tube, but the thickness of all the portions of the tube are the same. As shown in Figure 11, alternative mold designs are considered to be equally applicable to the previously described process. When discussing this alternative modality, the part numbers similar to those referenced use the same reference numbers previously described. Similar parts, although modified, are designated with the inclusion of a quote (') after the reference number. The device includes a horizontally operating, two-piece, vertically movable, top-holding die (9), a horizontally fixed, centrally located, two-piece horizontally operating mold (10 ') and a mold (11'). ) vertically movable. The fastening die (9) includes a central bore, the diameter of which is equal to the diameter sufficiently smaller than the diameter of the tube to be widened so as to cause a clamping effect of the tube when the die is closed ( 9) Clamping. The mold (10 ') operating horizontally of two pieces, vertically fixed, central, includes a central perforation, of the same diameter of the tube to be enlarged. The lower end of the perforation is provided with a conical flared portion (15), the lower end of which is of a diameter and length equal to the outer diameter and length of the enlarged end of the tube. The lower mold (11 ') includes a body (20) which can include an annular conduit (21) for the circulation of cooling medium therethrough. The body is threadably connected to the rod (22) of a piston-cylinder assembly and is adjustably fixed thereto by a nut (23). The lower mold or punch (11 ') is provided with a central recess that is generally shown with the number (25) within which the axial projection (14') of the upper mold (10 ') is designed closely for telescopic coupling. Projecting from the bottom of the recess (25 ') is the rod (30'), the diameter of the rod in the lower portion of the recess with a diameter equal to I.D. of the enlarged end of the tube and maintained by a distance equal to the depth of the tube's widening. The rod (30 ') terminates in the upper part (31') and has a radius corresponding to the corresponding conical flared portion (15), in the conical segment (32). In the sequenced operation, and shown in the successive figures, this modified mold and die design are identical in concept and implementation to those previously detailed and all the related discussion is equally applicable to any modality. As shown in Figure 12, the plastic (37) is inserted through the holding mold (9) and the upper mold (10 '), which rests on the tube position stop (40). The two halves of the holding mold (9) are thus closed by firmly retaining the plastic (37). In Figure 13, the holding mold (9) is moved to a position extending to the lower end of the plastic (37) in a cavity in heating blocks (42). The divided halves of the central mold (10 ') close around the circumference of the plastic body (37) during the heating cycle to provide stability to the tube during the heating cycle. With the heating cycle completed, the central mold (10 ') is opened and the clamping mold (9) returns to its original decoupled position. The heated end of the plastic (37) is now placed in the enlarged cavity of the central mold (10 ') as shown in Figure 14. In Figure 15, the central mold (10') has been closed around the plastic (37). ) and the lower mold (11 ') has moved upward with the pilot tip (31') of the guide rod (30 ') penetrating the heated end of the tube. In Figure 16, the lower mold (11 ') extends completely, urging the heated plastic into the cavity created in the central connection mold (10') and the lower mold (11 '). After a sufficient period of cooling, all the molds return to their original positions and the enlarged tube is then removed from the molds. Figure 7 illustrates an embodiment of a completed pipe connector (70) comprising a unitary molded end cap (80), a nut (100) and a widened end (75). The length of the connector (70) is of any length and configuration. It can be straight or contain a myriad of curvatures and torsions. However, what is critical is that subsequent to the formation of the end cap (80), the nut (100) is placed on the connector with the open face (92) of the nut (100) facing the cap (80) end. It is not possible to insert the nut (100) subsequent to the spreading step previously described. The unitary molded end cap (80) comprises a widened sealing surface (84) extending from the end face (82) of the tube to the radially extending flange (86). The sealing surface (84) can be radiated as indicated or can be conical. The end face (82) of the tube has an O.D. slightly larger than the rest of the tube so that the wall of the tube on the sealing surface is substantially enlarged through its length. The sealing surface terminates in the flange (86) which includes a stop face (85) adjacent to the sealing surface and a flange (88) on the opposite side. From the ledge to the O.D. of the tube, a chamfer (90) is provided which joins the flange separate from the peripheral edge thereof with any of the light spokes (65), as shown in Figure 6, or a collar (90) as shown in FIG. Figure 7. The nut (100) which is inserted before the spreading step, and after the formation of a unitary molded end cap (80) is placed on the connector (70) of diameter (dx) through the opening (102) of the nut which is larger in diameter than (dx), but smaller in diameter than the flange (86), with the open face (92) placed towards the lid (80) ) of end. The nut (100) contains a threaded circular bore (104) of predetermined height (94) which is used to sealingly engage a matching threaded receiver. (not shown). As the nut (100) is tightened by a plurality of parallel spaced edges (96), the end cap (80) is put in leak tight engagement with the receiver threaded by the upper surface (98) of the nut (100), through its coupling in the flange (88) of the lid (80) end, as best seen in Figure 8. In an embodiment of this invention, shown only in Figure 7. The retaining edges (99) are compression molded in the body of the tube, which serve with the purpose of retaining the nut (100) close to the molded end cap (80). Due to the flexible nature of the initial thermoplastic material, the nut (100) is capable of being inserted on the retention ridges (99) by the application of light pressure. The precise placement of the retaining edges is not critical, but is generally in close proximity to the sealing end of the tube. Edges are molded into the pipe design through a simple modification of the mold design used to fabricate the sealing end. The amount of retaining edges can be variable, with at least one, preferably at least two, opposing nodes being in the body of the tube. A greater number of retention edges is also considered within the scope of this invention, the number will depend both on cost and geometrical space considerations. In this way, the connector (70) of unitary construction, of original diameter (dx) and thickness (t), which, through the heating process and molded inside an appropriately configured die, is shaped in the lid (80). ) end, even in diameter (d-) After the insertion of the nut (100) and subsequent heating of an opposite end to the end cap (80) of the connector (70), followed by molding in a second configured die suitably, the enlarged end (75) is fabricated of larger diameter (d2) but still of thickness (t) As shown in Figure 9, the plumbing connector (70) need not be in a linear configuration along the length of A longitudinal axis of the connector In fact, non-linear configurations are within the scope of the invention Such curvatures within the connector may be: (1) permanent, the result of post-fabrication techniques, such as mild localized moderate heating at a softening point of the material, followed by bending and molding within a facility that will retain the desired angle and radius, followed by cooling, and other processes which are known in the art; or (2) not permanent. Although the wall thickness (t) of the plumbing connector has been shown to be the same throughout the process, the application is not necessarily limited to such. As shown in Figure 10, it is possible to manufacture a plumbing connector (70) in which the thickness of the wall (t ') is greater than that of the middle portion of the tube (37). In other words, (f) > (t). Such a configuration is elaborated by increasing the thickness of the die cavity containing the circular bulb forming the cavity 28. As discussed previously in relation to a constant wall thickness (ü), the thickness (tr) will require that the tube (37) ) project an even longer distance below the upper mold (10) than that used when the thickness (t) is desired. This is necessary so that subsequent to the softening of the projected end of the tube (37) via the action of the heating blocks (42) and (43), or other heating means, and the dies have been put together, it will be filled with polyolefin a larger die space, that is, the bulb-forming cavity (28).

Although the unitary molded end cap (80) has been previously prepared according to the mold design shown in U.S. 4,316,870, U.S. 4,446,084 and U.S. 4,525,136, is not limited to such forms. It should be recognized that although a molded end cap such as that shown in Figures 7-10 may be highly desirable when polybutylene is used, the crosslinked polyethylene may be significantly harder and more rigid, or softer and more flexible, and possesses Different sealing characteristics. In some cases, that is, in an alternative embodiment, it is preferable to change to a different mold design for the molded end cap, so as to produce a pipe end (110) as shown in Figure 17 where shows a diameter (dx) of constant tube having a thickness (t) of pipe wall and a tip cone shelf (106) projecting essentially normal or perpendicular to the longitudinal axis of the pipe, as shown. The sealing bulb (108), shown in cross section, is a separate insert which is housed in itself on one side of the tip cone shelf (106), and is typically made of a rubber polymer (e.g. EPDM, neoprene, TPR, TPE, etc.) which is softer than cross-linked polyethylene. The pipe end shown in Figure 17 is different when contrasted with the design which has been used in the prior art when the cross-linked polyethylene is the pipe material, as shown in Figure 18. The shelf (112) tip cone is actually a component of a metal insert (116) which is held in place via a metal or plastic ring (114) which adjusts by compression (tight) or shrunk on the outside of the tube. The metallic insert (116) is of diameter (d3) which is slightly larger than the I.D. in comparison with the I.D. of the original tube (d2). This prior art product is inherently weaker than the molded end cap because any tight fit can potentially be separated which leads to field failure. Although piping connectors have generally been shown to have a molded end and a flared end, there is no need to limit the invention to such. In fact, depending on the proposed application, it may be highly desirable to have two molded ends (130), as shown in Figure 19 or two flared ends. The connector (130) is an example of a connector with two molded ends (134, 154), one end is conical (136) and has a shelf (138) with the other end (152) rounded. The connector is of multi-layer construction having an internal cross-linked thermoplastic layer (142), with a superimposed layer (116) of stainless steel, attached to the conical end via a metal ring (140) and the end rounded by a ring (150). ) metallic. Each ring also contains a means (132, 148), in this example, it is a nut threadably engageable.

Based on the available equipment, the polyolefin pipe (eg, polyethylene), is crosslinked using conventional means known to those familiar in the art (eg, silane, radiation, etc.). The material typically reticles to at least 60% with amounts as high as 85% as possible. The cost usually decides which crosslinking method needs to be used to provide a given quality of pipe. The benefit of crosslinking the polyethylene subsequent to the manufacturing steps described in the application is that the bonding of the chemical material is formed during the final forming compression molding processes, resulting in a more resistant product. However, there may be applications where this type of final training is not essential, so that the use of previously reticulated material is allowed during the manufacturing process. The previously cross-linked material has a much better heat-fusion resistance since the crosslinking provides more structure, and makes the training easier. However, the crosslinked material will not chemically bond itself even when heated to the transparent state. This does not mean that the material at the formed ends does not seal completely on itself, but is molded in place with pressure. Of course, the lattice can be carried out in many different ways. Most of the crosslinking is done in extrusion processes, specifically by the Engel process, the silane process or the peroxide process. Each process has a crosslinking catalyst that causes the polymer to form a crosslink when a certain temperature and pressure is used. An additional way to crosslink is to use radiation. In this method, the extruded tubes pass under a radiation unit and the exposure causes crosslinking. It is usually more economical to radiate straight tubes since it is related to how many parts will be placed in a diagram that rotates under the beam. However, this does not represent the only modality contemplated within the invention. It is considered that, under certain circumstances, it would be appropriate to crosslink the final product. Although sequencing of the processing steps mentioned above is generally not critical, certain aspects need to be performed in sequence, for example, the flare and flare sequences discussed previously in this application. Based on the physical strength and integrity of the final product, the stages of cross-linking, widening and / or flared can be carried out in any sequence, the only limitation is that the insertion of a nut is made before completing the manufacturing processes both widened and flared. A similar limitation will also be present when the pipe work piece must have two sealing surfaces at opposite ends. The insertion of the nut needs to precede the manufacture of the second sealing end.

Discussion What has been described is a thermoset tube instead of thermoplastic which has a much higher heat distortion temperature when compared to standard thermoplastic materials such as polybutylene, polypropylene, polyethylene, ABS or PVC. The resistance to stress fracture is greater as well as the dimensional stability. These desirable properties can be obtained by using a lower cost material, in contrast to a more expensive thermoplastic. Through the processing described above, a superior product can be manufactured at a lower price than is possible using a standard thermosetting, which has not been processed in a similar way (the thermoset materials can not be extruded). The invention uses thermoplastic processing conditions, with subsequent crosslinking to form a thermosetting material. This combines the best features of both types of materials: (1) the ease of thermoplastic processing; combined with (2) the desirable physical properties of a thermosetting material. One of the biggest advantages with the use of crosslinked polyethylene is the fact that it is not sensitive to notches, a physical property of great concern when using polybutylene.

Other significant advantages associated with the use of cross-linked polyethylene when compared to polybutylene are based on the fact that the cross-linked polybutylene is not a crystalline material. Polybutylene, for example, requires seven days after extrusion to crystallize and the molded ends can not be formed until this time. The crosslinked polyethylene can be formed immediately. The crosslinked polyethylene has a higher heat distortion temperature and is therefore at least 60% crosslinked, and can not be used as a regrind material. There is a significant memory effect associated with the crosslinked polyethylene and the material always returns to its original shape when it is crosslinked. The PEX can be lower density polyethylene and when reticulated, it will result in a softer and more flexible tube. PEX is also a more tolerant material to manufacture ends in what is possible to form in radios and later manufacture. Therefore, what is shown in this application is that through process modifications, the inherent limitations in polyethylene, polypropylene and polybutylene have been resolved. Polyethylene is a low cost product that is easy to process, but suffers from low temperature resistance, low resistance to discharges and little resistance to progressive deformation. It has good flexibility. Polypropylene is of moderate cost and is also easy to process. However, it has little resistance to impact in a cold environment, little resistance to progressive deformation, little resistance to discharge and little flexibility. Polybutylene is high cost and difficult to process, but has good impact resistance in cold environment, good resistance to progressive deformation, good resistance to discharge, but suffers from little flexibility. When working with a medium density polyethylene, which is low cost, easy to process, good flexibility but with marginal cold impact and low resistance to discharge, and crosslink the material to more than 65%, the resulting product possesses good resistance to progressive deformation, good flexibility, good resistance to discharge, good impact to the cold environment, a significantly lower cost compared to polybutylene and a higher heat distortion temperature with a double life expectancy than polybutylene. The key when forming the ends lies in the processing that takes place when the material is crosslinked, since it becomes a thermosetting material in opposition to a thermoplastic material when it is extruded. In order to solve this limitation, the molding temperatures are increased to a higher processing temperature, pressure is added because the material must be formed on itself, which is flexible, but does not stick to itself. When the material is crosslinked at 65%, only 35% remains for bonding. The waste is not reprocessible, so the operations must be more exact and the pipe must be constantly checked to ensure that the reticulation takes place. The amount of pressure depends on the material which is processed, the exact number of kilos or pounds of pressure varies until the molded product evenly fills the mold. By combining the innovation of extrude and then irradiate, superior properties have been developed at a competitive cost. By combining all of the above, a completely different product is formed which is thermostable instead of a thermoplastic. The invention has been described with reference to preferred and alternative embodiments. Evidently, modifications and alterations will occur to other people when reading and understanding the specification. It is intended to include all such modifications and alterations insofar as they fall within the scope of the appended claims or the equivalents thereof.

Claims (35)

WHAT IS REVINDED IS:

1. A process for forming a unitary molded tubular connector having at least one end cap integrally molded with a first diameter at one end of the connector, a tubular segment having a first internal diameter equal to that of the end stage and a first outer diameter and a thickness measured as the difference between the first inner diameter and the first outer diameter, the tubular segment originates from the end cap, the connector is formed from a hollow cylindrical tube of uniform thickness of the same thickness as the tubular segment , the process is characterized in that it comprises the steps, without considering the order of steps (a) and (b): (a) molding an end cap comprising the steps, in the following order, of: (i) inserting a The first end of the tubular connector through the female end cap die, the die surrounds the first outer diameter of the tubing connector and has an adaptive cylindrical projection to cooperate with a recess of a male end cap die; (ii) retaining the tubular connector from the female end cap die with the end cap so that they project from the female end cap die, the male and female end cap dies are separated; (iii) heating the portion of the tubular connector projecting from the female end cap die sufficiently to make such a projection portion sufficiently flexible for forming; and (iv) forming the heated portion of the tubular connector in an end cap by cooperating the cylindrical projection of the female end cap die and the recessing of the male end cap die when closing the female and male end cap punches. , the end cap further comprises: an end face, a sealing means and a flange having a protrusion and further having an opening centrally positioned therethrough; and (b) crosslinking the tube with a crosslinking agent.

2. The process according to claim 1, characterized in that it further comprises inserting at least one clamping means in the tubular connector, the clamping means has an opening centrally positioned therein, the opening is adapted so as to allow insertion on the first outer diameter of the tubular segment, still smaller than the anterior diameter of the flange of the end cap, the fastening means further comprises a threaded end, the threaded end being adapted for sealing engagement on the molded end.

3. The process according to claim 1, characterized in that step (iv) further comprises forming the heated portion of the tubular connector in an end cap by cooperating the recess of the end cap die 5 male and the cylindrical projection of the female end cap die, the male end cap die has a shape so as to form a sealing means which is selected from the group consisting of a curved sealing means and a conical sealing means.

4. The process according to claim 1, characterized in that it further comprises the insertion of a separate sealing means which is softer than the tubular connector on the end face of the lid so as to form a cone 15 of tip.

5. The process according to claim 1, characterized in that it also comprises the step of inserting a braided envelope.

6. The process according to claim 1, characterized in that the molded tubular connector is polyethylene and the temperature of step (iii) is approximately 371 ° C (700 ° F) for about 15-25 seconds.

7. The process according to claim 6, characterized in that it includes the additional step of cooling the tubular connector after step (iii).

8. The process according to claim 7, characterized in that it further comprises: the step of physically pushing the heated portion into the connector within the male and female end cap dies under the conditions of molten flow so as to uniformly fill the dies.

9. The process according to claim 1, characterized in that the step of crosslinking the tube occurs after step (a).

10. The process according to claim 1, characterized in that the step of cross-linking the tube is the first stage of the process.

11. The process according to claim 1, characterized in that the crosslinking agent is selected from the group consisting of the Engel process, the silane process, the peroxide process and irradiation.

12. The product, characterized in that it is produced by the process according to claim 1.

13. The process according to claim 1, characterized in that it further comprises the step of inserting two clamping means on the tubular connector after step (iv) and repeating steps (i) to (iv), the clamping means has a opening centrally therein, the opening is adapted to allow insertion on the first outer diameter of the tubular segment, which is still smaller than an outer diameter of the flange of the end cap, the fastening means further comprises a threaded end , the threaded end is adapted for sealing engagement on the molded end.

14. The process according to claim 13, characterized in that step (iv) further comprises forming the heated portion of the tubular connector at one end by cooperation of the recess of the male end cap die and the cylindrical projection of the female end cap die , the male end cap die has a shape so as to form a sealing means which is selected from the group consisting of a rounded sealing means and a conical sealing means.

15. The process according to claim 13, characterized in that it further comprises the insertion of a separate sealing means which is softer than the tubular connector on the end face of the end cap so as to form a tip cone.

16. The process according to claim 13, characterized in that it further comprises the step of inserting an overbraiding after the insertion of the first fastening means.

17. The process according to claim 13, characterized in that the molded tubular connector is polyethylene and the temperature of step (iii) is about 135-168 ° C (275-335 ° F) for about 20-30 seconds.

18. The process according to claim 17, characterized in that it includes the additional step of cooling the tubular connector after step (iii).

19. The process according to claim 18, characterized in that it further comprises the step of physically driving the heated portion of the connector in the male and female end cap dies under conditions of molten flow so as to uniformly fill the dies.

20. The product, characterized in that it is manufactured by the process according to claim 13.

21. The process according to claim 1, characterized in that it further comprises the formation of an opposite widened tubular end having a second larger internal diameter and a second outer diameter, the thickness of the enlarged end is at least the same thickness as that of the segment tubular, and a fastening means having an opening centrally positioned therein, the opening is adapted to allow insertion on the outer diameter of the tubular segment, and is still smaller than the outer diameter of a flange of the end cap and the outer diameter of the enlarged end, by: (i) inserting at least one clamping means on the tubular connector, the clamping means has an opening centrally positioned therein, the opening is adapted so as to allow insertion on the first outer diameter of the tubular segment, but it is still smaller than the external diameter of the flange of the tap at the end, the clamping means further comprises a threaded end, the threaded end is adapted for sealing engagement on the molded end; (ii) inserting a second end of the tubular connector through the female expansion die, the die encloses the first outer diameter of the tube and has a cylindrical projection adapted to cooperate with a recess of the male enlarging die; (iii) retaining the tubular connector from the female flare die with the flared end so that it projects from the female flare die, the male and female flare dies are separated; (iv) heating the portion of the tubular connector projecting from the female flare die sufficiently to make such a projection portion flexible enough to be formed; and (v) forming the heated portion of the tubular connector at the enlarged end of the second of the inner and outer diameters, which have at least the same thickness as the tubular connector, by cooperating projection of the male flange die and the recess of the male flare die when closing the female and male flare dies.

22. The process according to claim 21, characterized in that it further comprises the step of: placing the second end of the tubular connector partially on an elongated male flare die projection of the male flare die, with the projection closely matching the first diameter internal of the tubular connector, the male flange die includes a recess which increases from the first internal diameter to the second internal diameter and which increases correspondingly from the first outer diameter to the second outer diameter so as to maintain at least the same thickness , from which the male die projection projects axially and concentrically, before stage (iv).

23. The process according to claim 21, characterized in that it also includes the additional step of cooling the tubular connector after step (v).

24. The process according to claim 21, characterized in that it further comprises the step of physically driving the heated portion of the tubular connector in the male and female flare dies under the conditions of molten flow so as to uniformly fill the dies.

25. The process according to claim 24, characterized in that it further includes the step of cooling at least one of the male and female enlarging dies after they are joined in step (iv) of claim 21.

26. The process according to claim 21, characterized in that the molded tubular connector is polyethylene and the temperature of step (iii) is about 371 ° C (700 ° F) for about 15-35 seconds.

27. The product, characterized in that it is made by the process according to claim 21.

28. A process for forming at least one enlarged tubular end without thinning the walls from a constant thickness portion of a hollow cylindrical tube, characterized in that it comprises the steps, without considering the order, of steps (a) and (b) ): (a) molding an enlarged end comprising the steps, in the following order: (i) inserting one end of the tubular connector through a female flange die, the die encircles a first outer diameter of the tubular connector and has a cylindrical projection adapted to cooperate with a recess of a male flare die; (ii) retaining the tubular connector from the male flare die with the flared end so that it projects from the female flare die, the female and male flare dies are separated; (iii) heating the portion of the tubular connector projecting from the female flare die sufficiently to make such projection portion flexible enough to be formed; and (iv) forming the heated portion of the tubular connector at the enlarged end by cooperation of the recess of the male flare die and the projection of the female flare die when closing the female and male flare dies; and (b) crosslinking the tube with a crosslinking agent.

29. The process according to claim 28, characterized the molded tubular connector is polyethylene and the temperature of step (iii) of claim 28 is about 371 ° C (700 ° F) for about 15-35 seconds.

30. The process according to claim 29, characterized in that it also includes the additional step of cooling the tubular connector after step (iii).

31. The process according to claim 30, characterized in that it further comprises the step of physically driving the heated portion of the connector into the male and female flare dies under molten flow conditions so as to uniformly fill the dies.

32. The process according to claim 31, characterized in that it further includes the step of cooling at least one of the male and female enlarging dies after they are put together in step (iv) of claim 28.

33. The product, characterized in that it is made by the process according to claim 28.

34. The process according to claim 1, characterized in that it further comprises the step of: partially placing the first end of the tubular connector in an elongated male die projection of the male end cap die with the projection tapering closely to the first internal diameter of the connector tubular, the male end cap die includes a recess from which the male die portion projects axially and concentrically prior to step (iii) of claim 1.

35. The process according to claim 28, characterized in that it further comprises the step of: placing one end of the tubular connector having a first internal diameter and a first outer diameter and a thickness, measured as the difference between the first internal diameter and the first outer diameter, partially on an elongated male die projection of a male flare die, the projection closely conformed to the first internal diameter of the tubular connector, the male flare die includes a recess which increases from the first internal diameter to the second inner diameter and correspondingly increases from the first outer diameter to the second outer diameter, so as to maintain at least the thickness, from which the male die projection projects axially and concentrically, before the step (iii).