A PLASTIC PIPE AND METHOD FOR MANUFACTURING A PLASTIC PIPE OF THIS TYPE

Abstract: A plastic pipe part 1 comprising longitudinally extending channels 4 in its wall, spinwelded to a widened end portion 8, 8′ and spigot end portion 20, respectively which present a conically extending welding surface 9, 9a, having a top angle comprised between 90 and 160°. For centering purposes the widened end portion 8, 8′ and spigot end portion 20 respectively may be provided with a circumferential project­ ing edge part 16, 16a. The widened end portion 8′ may be provided with channels formed by partitions 25. Inner annular surface 15 is machined for removing a welding ridge. For the spinwelding method the plastic pipe part 1 is provided with a front portion 7 extending perpendicularly to the axis of pipe part 1.

Description: A PLASTIC PIPE AND METHOD FOR MANUFACTURING A PLASTIC PIPE OF THIS TYPE BACKGROUND OF THE INVENTION The invention relates to a plastic pipe part comprising longitudinally extending channels in its wall and provided with an end portion in the form of a socket end portion or spigot end portion suitable for forming a spigot socket connection. A plastic pipe of this type, comprising longitudinally extending channels in its wall and being provided with a socket end, is known in the art. The socket end of such a plastic pipe is formed by heating an end portion of the plastic pipe and subsequently pressing the inner and outer walls of the channels of the plastic pipe upon each other, the end of said plastic pipe whether or not being subjected to a rotational motion during said action. The spigot end is formed in the same manner, simultaneously with a chamfer to facilitate pushing said spigot end into a socket end. Said known plastic pipe presents the disadvantage that the formation of the socket end and spigot end is rather timeconsuming and cumbersome. It is an additional disadvantage of the known pipe that the obtained end portion, more particularly the front end portion of the socket end or spigot end, often has an irregular shape while the impact strength is less than that of an undeformed pipe. Furthermore, the selection of the diameter of the socket end portion is bounded to the diameter of the plastic pipe. SUMMARY OF THE INVENTION The present invention aims to provide a plastic pipe of the abovementioned type in which the shape of the socket end portion is no longer bounded to the diameter of the plastic pipe, while a socket end portion and spigot end portion, respectively to be formed to such a plastic pipe can be provided in a much easier manner and the obtained plastic pipe additionally possesses optimum impact properties. This object is achieved according to the invention in that the socket end portion, spigot end portion, respectively, has been obtained by spinwelding a widened end portion, the spigot end portion respectively, to the front end of initial plastic pipe part. To obtain this kind of plastic pipe any type of widened end portion being connected to the front end of the plastic pipe part by means of spinwelding, can be used. The operation results in plastic pipes comprising socket end portions which are obtained in a very rapid manner and can optimally be adapted to the desired type of application. Very conveniently, a projecting annular edge part on the outer side of the plastic pipe extends to beyond a transition weld surface formed between the widened end portion and the front end portion of the plastic pipe. ihe initial plastic pipe part and the widened end portion particularly consist of a polyvinylchloride or a modified polyvinylchloride, having equal or differing K-values. However, the invention is not restricted to this type of plastic. The invention also relates to a method for manufacturing a plastic pipe part comprising longitudinally extending channels in its wall and provided with an end portion in the form of a socket end portion or spigot end portion, suitable for forming 5 spigot-socket connection, said method being effected according to the invention in that the front end of an initial plastic pipe part, comprising longitudinally extending channels in its wall, is spinwelded to a widened end portion, spigot end portion, respectively. To form a socket end very advantageously an initial widened end portion is used, provided with a truncated conical welding surface, the extension thereof forming a cone having a top, positioned within the circumference or the extension of the widened end portion, and the top angle being comprised between 900 to 1600 and preferably amounting to about 1300. A subsequent spinwelding operation will in a very short period of time effect an optimum connection between the plastic pipe and the widened end portion, spigot end portion respectively. Additionally the channels in the pipe wall at the site of the socket end portion, are effectively sealed. To form a spigot end portion, preferably a full walled initial pipe portion is employed having an outer and an inner diameter substantially corresponding to the initial channel walled plastic pipe, said full walled pipe portion being provided with a truncated conical welding surface, the extension thereof forming a top being disposed within the circumference or the extension thereof of the fullwalled portion, the relative top angle being comprised between 90 to 1600 and preferably amounting 0 to about 130 Preferably, the front end of the initial pipe portion for forming the socket end portion, spigot end portion respectively, extends substantially perpendicularly to the axis of the initial plastic pipe. DESCRIPTION OF THE DRAWINGS: - Fig. 1 is a plastic pipe with a socket end portion, obtained according to the invention; - Fig. 2 is a widened end portion to be spinwelded to the front end of an initial plastic pipe, for forming a plastic pipe with a socket end portion according to the invention; - Fig. 3 is a sectional view according to line Ill-Ill in fig. 1; - Fig. 4 is a longitudinal view on an enlarged scale of part of the plastic pipe at the location of a longitudinally extending channel: : - Fig. 5 is a similar sectional view as in fig. 4, at the site of a connecting wall; - Fig. 6 is a plastic pipe with a spigot end portion, obtained according to the invention; - Fig. 7 is an initial fullwalled pipe portion to be spinwelded to the front end of a plastic pipe to form a plastic pipe com prising a spigot end portion; - Fig. 8 is a longitudinal sectional view of a hollow spigot end portion and - Fig. 9 is a longitudinal sectional view of a hollow widened end portion. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 illustrates a plastic pipe part comprising longitu dinally extending channels 4, formed by walls 5 being integral with the inner wall 3 and the outer wall 2 of the plastic pipe. The plastic pipe comprises a socket end portion 6 formed by spin weldingafullwalled widened end portion 8 to pipe part 1. The fullwalled widened end portion 8 is advantageously pro vided with a widened region 18 for receiving a sealing sleeve, the head of the latter being retained by a retaining ring, en gaging the elevations 19 provided on the outer side of the widened end portion 8. To obtain a good connection by means of spinwelding, the initial plastic pipe 1 is provided with a front end 7 extending substantially perpendicularly to the axis of the initial pipe, the widened end portion 8 being provided with an adjoining welding surface 9 in the form of a truncated cone. Fig. 2 illustrates that the extension of the truncated conical welding surface 9 forms an imaginary cone, the top 12 of same being disposed within the widened end portion. The top angle of the top 12 of said cone is advantageously comprised between at most 1600± and at least 90 C, said top 0 0 angle preferably being comprised between 110 - 150 and, more preferably, amounting to 1300. During the spinwelding operation material 30 of the outer wall 3 is substantially pressed into the channels 4, as illustrated in fig. 4. This results in an optimum connection between the initial plastic pipe part and the widened end portion 8 and additionally, at that location an extremely good seal of the channels 4 in the wall of the plastic pipe part 1. The outer side of the widened end portion 8 is provided with a projecting annular edge part 16, which extends after the spinwelding operation, to beyond a weld transition surface 10 formed between the welding surface 9 and front end portion 7 of the plastic pipe 1. Said annular edge portion 16 is used for centering front end portion 7 with respect to widened end portion 8 at the start of the spinwelding operation, and for covering the obtained weld in the finished plastic pipe with socket end portion . Said annular edge part 16 moreover, supports an end part 11, extending substantially perpendicularly to the pipe axis and merging into the outer wall of the widened end portion 8 through a truncated conical wall 17. The welding transition surface 10 terminates into a tapering inner wall part 15 of the widened end portion 8 having an inner diameter substantially corresponding to the inner diameter of the pipe 1. For the welding operation an initial widened end portion 8 is used, comprising a tapering inner wall part 13 adjoining the truncated conical welding surface 9 and having a diameter corresponding to or smaller than the inner diameter of the plastic pipe part 1. This creates the possibility of using the same widened end portion 8 for pipe parts having corresponding outer , but differing inner diameters. Any redundant material and/or weld ridges, may be removed by machining the inner wall portion so that a smooth inner wall portion 15 is obtained, having a diameter corresponding to the inner diameter of the pipe part 1. The pipe part 1 and the widened end portion 8 particularly consist of a polyvinylchloride or modified polyvinylchloride having identical or differing K-values. Fig. 7 illustrates an initial plastic pipe 1, being spinwelded to a fullwalled pipe part 20, said pipe portion 20 on the one hand sealing the channels 4 and on the other end functioning as a spigot end portion. The fullwalled pipe portion 20 is advantagously provided with an end chamfer 21. The inner and outer diameter of said full-walled pipe portion 20 substantially correspond to the inner and outer diameter of the initial plastic pipe 1. Said pipe portion 20 is also provided with the aforementioned truncated conical weld surface 9, the front end portion 7 of the initial plastic pipe 1 extending substantially perpendicularly to the pipe axis. To realize the relative centering conical weld surface 9is advantageously adjoined by an annular edge part l6s, obtained by an annular outer thickened wall part 22, upon the outer side of a full-walled pipe portion 20. After the spinwelding operation any weld ridges being present on the inner side of the assembly illustrated with dotted lines may be removed by machining. EXAMPLE 1 To obtain a plastic pipe comprising a spinwelded widened end portion, use is made of an initial, extruded plastic pipe part 1, comprising longitudinally extending channels 4 and consisting of polyvinylchloride havinga K-value comprised between 65 and 75 and of an injection-moulded widened end portion 8 of polyvinylchloride having a K-value of 70. With respect to the plastic pipe 1, widened end portion 8 is rotated with a circumferential velocity of 2 m/sec In a first step a line contact is provided between the outer side of the front surface 7 and a welding surface 9, so that plastic material 30 from the outer wall 3 of the plastic pipe 1 is pressed into the channels 4. In a second step the actual spinweld joint is formed while still rotating and exerting a pressure. In a third step the spinwelding operation is terminated, and cooling under a pressure of, for instance, 6 kgf/cm2 is effected, whereupon a part 13 projecting outside the inner wall of the initial pipe 1 is removed. EXAMPLE II Example 1 is repeated, however, with a full-walled pipe portion 20, thus providing initial plastic pipe with a fullwalled spigot end portion sealing the channels 4, a penetration of such a spigot end portion 20 into a socket end being facilitated by the end chamfer 21 (see fig. 8). EXAMPLE III Example II is repeated, but use is made of partially hollow, injection-moulded spigot end pipe portion 20', Said spigot end pipe portion therefore comprises an outer wall 20a and an inner wall 20b (fig. S illustrates a longitudinal section of such a portion 20') one end of said walls being sealed by a bottom 24 forming an end chamfer 21. Partitions 23 have been formed by the injection moulding operation and comprise ends 27 forming together with an inner wall end 28 and outer wall end 29 an imaginary welding surface 9a (see fig. B). A spinwelding operation results in an extremely good con nection and considerable economies on plastic material; by employing a pipe portion 20' additionally a notable weight reduction is obtained. In certain cases it may be recommended to remove edge part 16a as used for the centering operation, after the formation of the weld, so as to ensure an even outer diameter of the pipe portion 20' and the initial pipe. To obtain the desired spinweld joint, obviously instead of partitions 25, use can also be made of a thickened edge such as edge 22 positioned at the inner side of the outer wall and of the inner wall. EXAMPLE IV Exampleil is repeated, while using an at least partially hollow, widened end portion 8', the side walls of same may be interconnected by means of partitions 25 (as illustrated in fig. 9). An imaginary welding surface 9a is then formed by the free ends of the partitions, the inner wall and the outer wall surface of the widened end portion 8'.

Claims: WHAT IS CLAIMED IS: 1. A plastic pipe partlcomprising longitudinally extending channels4 inits wall and provided with an end portion in the 8,8' 20 20' form of a socket end portion or spigot end portion', suitable for forming a spigot-socket connection, wherein the socket end portion, spigot end portion, respectively, has been obtained by spinwelding a widened end portion, spigot end portion respectively to the front end7 of an initial plastic pipe part 1. 2. A plastic pipe part as claimed in claim 1, in which prior to the spinwelding operation, the widened end portion8,8'spigotend 2020' portion'respectively, have been provided with a truncated coni- cal welding surface and preferably prior to the spinwelding operation, the front end portion7ofthe initial plastic pipe 1 extended substantially perpendicularly to the axis of an initial pipe part 1. 3. A plastic pipe part as claimed in claim 1, in which the widened end portion 8'spigot end portio respectively, comprise at least partially hollow walls and/or a projecting annular 16a edge part on the outer side of the plastic pipe extends to beyond a transition weld sur face 10 fom between the widened end portion and the front end portion of the plastic pipe and/ or a projecting annular edge part 16a support¯n end surface 11 extending substantially perpendicularly to the pipe axis, preferably the end surface of the annular part of the widened end portion merges into the outer wall of the widened end portion8 through a truncated conical wall 17. 4. A plastic pipe as claimed in claim 1, in which the welding transition surface lOterminates into a tapering inner wall part 15 of the widened end portion 8 the spigot end pipe portion 2D, 20' respectively, the inner diameter of which substantially corresponding to the inner diameter of the pipe part and preferably the tapering inner wall part .15 has been machined. 5. A plastic pipe part as claimed in claim 1, in which the plastic pipe and the widened end portion, spigot end portion respectively, consist of a polyvinylchloride or a modified poly vinyichioride having identical or differing K-values and/or plastic material 30 pressed away during the spinwelding operation has been received in the channels 4. 6. A plastic pipe part as claimed in claim 1, in which a) in the completed weld between a spigot end pipe portion and an initial plastic pipe, the outer diameter of the transition surface and of both parts, the pipe part and spigot portion substantially correspond to each other, the transition surface of the outer side of the spigot end pipe portion has been machined and/or b) the inner diameter of the spigot end pipe portion of the initial plastic pipe and of a machined transition 15 surface, inner wall portion respectively, substantially correspond to each other and/or c) extension of the conical welding 9,9a surface forms a cone having a top angle of at least 900 and at most 1600, more preferably comprised between 1100 and 150 and/ or d) the top of the cone of the truncated conical welding 9, 9a surface is disposed within the widened end portion, spigot end portion respectively. 7. Method for manufacturing a plastic pipe part, comprising longitudinally extending channels in its wall and provided with an end portion in the form of a socket end portion or spigot end portion, suitable for forming a spigot-socket connection, in which a widened end portion, spigot end portion respectively is connected to the front end of the initial plastic pipe by spinwelding. 8. Method as claimed in claim 7, in which the widened end 8, Ba 20 20' portion, spigot end pipe portion Sespectively, are provided with a truncated conical weld surface and preferably prior to 7 the welding operation the front end portion of the initial 1 plastic pipe extends substantially perpendicularly to the axis of the initial pipe. 9. Method as claimed in claim 7, in which one or more of the following measures are applied: a) the widened end portion spigot end pipe portion respecti vely, comprise at least partially hollow walls; b) the widened end portion, spigot end pipe portion respecti vely, support a projecting annular edge part16, 16a; c) for spinwelding a spigot end portion to an initial plastic pipe, an initial edge part is employed forming a thickening upon the outer side of the spigor end portion, said thickening comprising said end part, may be removed after the spin welding operation and having an outer diameter substantially corres ponding to that of the initial plastic pipe, the spigot end portion and the transition thereinbetween; ; d) the inner side of the spigot end portion, the initial 10 plastic pipe, and the weld transition thereinbetween, have sub- stantially the same inner diameter; e) an annular edge partl6#ofa widened end portion is provided with an end suufacellextending substantially perpendicularly to the pipe axis and merging into the outer wall of the widened end portion through a truncated conical wall 17; f) the extension of the truncated conical weld surface forms a cone, the top of which is positioned within the widened end portion, spigot end portion respectively and the top angle of the top 12 the cone preferably amounts to at most 1600 and at least to 9û , preferably to 1300. 10. A method as claimed in claim 7, in which a) during the spinwelding operation, redundant material is pressed into the longitudinally extending channels 4disposed in the wall of the initial plastic pipe 1 and/or b) the welding surface 9 ofa widened end portion 8' terminates into a tapering inner wall part 15 having a diameter which is at most corresponding to the inner diameter of the plastic pipe 1 and /or c) the inner diameter of the initial tapering inner wall part 15 is smaller than the inner diameter of the plastic pipe and/or d) the plastic pipe part and the widened end portion, spigot end portion respectively, consist of a polyvinylchloride or a modified polyvinylchloride, having identical or differing K-values. 11. A method as claimed in claim 7, characterized in that after the spinwelding operation the tapering inner wall part 13 of the end portion 8 is so machined that its diameter substantially corresponds to the inner diameter of the initial plastic pipe 1 while forming a tapering inner wall part 15. 12. A widened end portion, spigot end pipe portion respectively, suitable for use in a plastic pipe as claimed in claims 1 to 6 and/or in a method as claimed in claims 7 to 11.

Inventors: LARSEN, CHRISTIAN, NIELSEN, UFFE DAN
Applicants: WAVIN B.V.
Application year: 1983
Main classification: F16L47
IPC codes: F16L47, B29C65, B29C53