Plastic pipeline having rapidly fusible joints and method of making same

• US 4,852,914 A
• Filed: 06/19/1987
• Issued: 08/01/1989
• Est. Priority Date: 06/19/1987
• Status: Expired due to Fees

• Current Assignee: Milfuse Systems Incorporated Santa FE Springs
• Original Assignee: Milfuse Systems Incorporated
• Inventors: Lyall, Lucian H.
• Primary Examiner(s): Arola, Dave W.
• Application Number:
  US07/064,114
• Time in Patent Office: 774 Days
• Field of Search: 285/21, 285/22, 285/423, 285/93, 219/535, 219/544
• US Class Current: 285/21.2
• CPC Class Codes: B29C 65/20 with direct contact, e.g. using "mirror"
• CPC Class Codes: B29C 65/342 comprising at least a single wire, e.g. in the form of a winding
• CPC Class Codes: B29C 65/3464 characterised by the cross-section of said heated elements which remain in the joint or by the cross-section of their coating, e.g. being triangular
• CPC Class Codes: B29C 65/3468 characterised by the means for supplying heat to said heated elements which remain in the join, e.g. special electrical connectors of windings B29C65/3668 takes precedence
• CPC Class Codes: B29C 65/348 with a polymer coating
• CPC Class Codes: B29C 65/72 by combined operations or combined techniques, e.g. welding and stitching
• CPC Class Codes: B29C 66/1142 Single butt to butt joints
• CPC Class Codes: B29C 66/1222 comprising at least a lapped joint-segment
• CPC Class Codes: B29C 66/1224 comprising at least a butt joint-segment
• CPC Class Codes: B29C 66/5221 for forming coaxial connections, i.e. the tubular articles to be joined forming a zero angle relative to each other
• CPC Class Codes: B29C 66/5344 said single elements being substantially annular, i.e. of finite length, e.g. joining flanges to tube ends B29C66/5346 takes precedence
• CPC Class Codes: B29C 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/81871 of the welding jaws
• CPC Class Codes: B29C 66/91411 of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29C 66/91653 by controlling or regulating the voltage, i.e. the electric potential difference or electric tension
• CPC Class Codes: B29C 66/91655 by controlling or regulating the current intensity
• CPC Class Codes: B29C 66/919 characterised by specific temperature, heat or thermal flux values or ranges specific electrical resistance values B29C66/81262
• CPC Class Codes: B29C 66/91933 higher than said fusion temperature
• CPC Class Codes: B29C 66/949 characterised by specific time values or ranges
• CPC Class Codes: B29C 66/972 by extrusion of molten material
• CPC Class Codes: B29K 2023/06 : PE, i.e. polyethylene
• CPC Class Codes: B29K 2023/065 : HDPE, i.e. high density polyethylene
• CPC Class Codes: F16L 47/03 : Welded joints with an electrical resistance incorporated in the joint

Abstract

A polyethylene pipeline including a plurality of prefabricated pipes of predetermined diameter fused on one end to respective bell fittings to form prefabricated bell and spigot pipe assemblies. The bell connector includes an enlarged in diameter bell connector formed with a socket having an internal diameter for telescopical receipt of the second end of the adjoining pipe length and includes an increased in diameter interior gland for receipt of a helical heating coil. The heating coil is constructed of an electrical resistant wire coated with an electrical insulative coating which is, in turn, coated with a medium density polyethylene coating. The terminal ends of the wire is coupled with electrical connectors protruding to the outside of the bell connector.

Claims

1. A rapidly fusible plastic pipe system comprising:

a plurality of thermoplastic pipes of a predetermined outside diameter, having a predetermined fusion temperature, and further having first and second ends;

a plurality of thermoplastic connection fittings having selected fusion temperature at least as high as said predetermined temperature and including respective necks prefused to said first ends of the respective pipes to form prefabricated pipe lengths and further including bell connectors formed with sockets for telescopical receipt of the respective second ends of the respective joining pipes, said bell connectors being formed medially in the respective sockets with heating coil-receiving glands;

helical heating coils formed from a length of coiled resistance wire coated with an electrically insulative coat, said insulative coat in turn coated with a thermoplastic fusion coat having a fusion temperature substantially the same as said predetermined temperature, said heating coils being nested in the respective glands and including terminal ends; and

a pair of electrical connectors embedded in the walls of the respective bell connectors and connected with the respective terminal ends,

whereby said prefabricated pipe lengths may be deployed at an installation site, said second ends rapidly telescoped into said sockets, and an electrical voltage applied across said connectors to heat said heating coils to said selected fusion temperature to rapidly melt said fusion coating to form a puddle of molten fusion material within the envelope formed between the respective gland and periphery of the adjoining pipe ends and continuing application of said voltage to continue to propagate heat rapidly through said molten material to the wall of said pipes and the wall of said bell connectors to fuse said second end in the respective sockets;

said bell connectors each including a wall section formed with an exterior radial recess defining a well terminating in a bottom wall spaced a predetermined distance from said heating coil, said predetermined distance being such that, when said pipe lengths have been telescoped together and said heating coils have been energized sufficiently long to generate sufficient heat to melt said fusion coating and the interior surfaces of the joining socket, said bottom wall will melt to give an indication that fusion has been completed.

2. A rapidly fusible plastic pipe system comprising:

a plurality of prefabricated thermoplastic pipe lengths, each pipe length characterized by a predetermined fusion temperature and including a first extremity having a predetermined outside diameter and a second extremity having an interior surface defining a bell socket adapted to telescopically receive the first extremity of another of said pipe lengths in close fitting relationship, the second extremity also having an exterior surface defining an indicator recess with a bottom wall spaced sufficiently close to the interior surface to melt when fusion is substantially complete;

a heating coil embedded in the second extremity of each pipe length adjacent the interior surface thereof; and

connection means in electrical communication with the heating coil and adapted for rapid connection to an electric power source,

whereby said pipe lengths can be deployed to an installation site, the first extremities of various ones of the pipe lengths can be telescoped into the bell sockets in the second extremities of various others of the pipe lengths to form a pipeline, and an electric power source can sequentially be connected to the various connection means to heat the corresponding heating coil to a sufficient temperature to rapidly fuse the pipe lengths together and disconnected when the bottom wall of the indicator recess melts, indicating that fusion is substantially complete.

3. A system according to claim 2 wherein each pipe length comprises a thermoplastic pipe characterized by said predetermined outside diameter and a thermoplastic fitting defining therein the bell socket, the fitting having a neck which is butt fused to an end of the pipe.

4. A system according to claim 2 wherein each heating coil comprises resistance wire coated with thermoplastic material.

5. A system according to claim 4 wherein the coatings comprise medium density thermoplastic and the second extremities of the pipe lengths comprise high density thermoplastic.

6. A system according to claim 5 wherein the resistance wire develops a temperature of at least 285 degrees Fahrenheit in its coating upon application of electric power having a predetermined voltage.

7. A system according to claim 6 wherein said temperature is developed within about one minute after application of the power.

8. A rapidly fusible plastic pipe system comprising:

a plurality of prefabricated thermoplastic pipe lengths, each pipe length characterized by a predetermined fusion temperature and including a first extremity characterized by a predetermined outside diameter and a second extremity fabricated of high density thermoplastic and having an interior surface defining a bell socket adapted to telescopically receive the first extremity of another of said pipe lengths in close fitting relationship, the bell socket including a gland adapted to receive a heating coil wherein the second extremity of each pipe length has an exterior surface defining an indicator recess with a bottom wall spaced sufficiently close to the interior surface to melt when fusion is substantially complete;

a heating coil fabricated of resistance wire coated with medium density thermoplastic and disposed in the gland; and

connection means in electrical communication with the heating coil and adapted for rapid connection to an electrical power source;

whereby said pipe lengths can be deployed to an installation site, the first extremities of various ones of the pipe lengths can be telescoped into the bell sockets in the second extremities of various others of the pipe lengths to form a pipeline, and an electric power source can sequentially be connected to the various connection means to heat the corresponding heating coil to a sufficient temperature to melt the medium density thermoplastic, the molten thermoplastic being operative to transfer heat from the heating coil to the first extremity of the pipe length in the socket and to the interior surface of the socket and thereby to rapidly fuse the pipe lengths together.

9. A rapidly fusible plastic pipe system comprising:

a plurality of prefabricated thermoplastic pipe lengths, each pipe length characterized by a predetermined fusion temperature and including a first extremity characterized by a predetermined outside diameter and a second extremity of high density thermoplastic having an interior surface defining a bell socket adapted to telescopically receive the first extremity of another of said pipe lengths in close fitting relationship;

a heating coil embedded in the second extremity of each pipe length adjacent the interior surfaces thereof, said heating coil comprising a resistance wire coated with medium density thermoplastic material;

connection means in electrical communication with the heating coil and adapted for rapid connection to an electric power source; and

a tactile fusion indicator formed in an exterior surface of the second extremity of each pipe length and operative to provide a tactile indication when fusion is substantially complete;

whereby said pipe lengths can be deployed to an installation site, the first extremities of various ones of the pipe lengths can be telescoped into the bell sockets in the second extremities of various others of the pipe lengths to form a pipeline, and an electric power source can sequentially be connected to the various connection means to heat the corresponding heating coil to a sufficient temperature to rapidly fuse the pipe lengths together and disconnected when the fusion indicator indicates that fusion is substantially complete.

10. A system according to claim 9 wherein the resistance wire develops a temperature of at least 285 degrees Fahrenheit in its thermoplastic coating upon application of electric power having a predetermined voltage.

11. A system according to claim 10 wherein said temperature is developed within about one minute after application of the power.

12. A method of constructing a plastic pipeline, the method comprising:

fabricating a plurality of fittings of high density thermoplastic material characterized by a predetermined fusion temperature, each fitting having a neck adapted for butt fusing to a thermoplastic pipe and an interior surface defining a bell socket adapted to telescopically receive a thermoplastic pipe characterized by a predetermined outside diameter in close fitting relationship;

embedding a heating coil in each fitting in a gland defined in the interior surface of the fitting, said heating coil comprising a resistance wire coated with medium density thermoplastic material and including connection means adapted for rapid connection to an electric power source;

fabricating a plurality of thermoplastic pipe lengths by butt fusing the necks of various ones of said fittings to various ones of plurality of thermoplastic pipes characterized by said predetermined fusion temperature, each resulting length having a first extremity characterized by a said outside diameter and a second extremity which includes one of said fittings;

deploying said pipe lengths;

deploying an electric power source;

telescoping the first extremities of various ones of the pipe lengths into the bell sockets in the second extremities of various others of the pipe lengths to form a pipeline; and

sequentially connecting the power source to the various connection means to heat the corresponding heating coil to a sufficient temperature to rapidly fuse the pipe lengths together and disconnecting the power source when the fusion is substantially complete.

13. A method according to claim 12 wherein the temperature to which the heating coil is heated is high enough to melt the thermoplastic coating, the molten thermoplastic being operative to transfer heat from the heating coil to the first extremity of the pipe length in the socket and to the interior surface of the socket.

14. A method according to claim 13 wherein the temperature to which the heating coil is heated is high enough to boil and thereby agitate the molten thermoplastic.

15. A method according to claim 13 wherein the steps of telescoping the first extremity of one of the pipe lengths into the socket in the second extremity of another of the pipe lengths and connecting the power source to the connection means of said second extremity to fuse the pipe lengths together and disconnecting the power source when fusion is substantially complete are accomplished in not more than about 90 seconds.

16. A method of constructing a plastic pipeline, the method comprising:

fabricating a plurality of fittings of thermoplastic material characterized by a predetermined fusion temperature, each fitting having neck adapted for butt fusing to a thermoplastic pipe and an interior surface defining a bell socket adapted to telescopically receive a thermoplastic pipe characterized by a predetermined outside diameter in close fitting relationship;

forming an indicator recess in an exterior surface of each fitting, the recess having a bottom wall spaced sufficiently close to the interior surface to melt when fusion is substantially complete;

embedding a heating coil in each fitting adjacent the interior surface, the heating coil including connection means adapted for rapid connection to an electric source;

fabricating a plurality of thermoplastic pipe lengths by butt fusing the necks of various ones of said fittings to various ones of a plurality of thermoplastic pipes characterized by said predetermined fusion temperature, each resulting length having a first extremity characterized by said outside diameter and a second extremity which includes one of said fittings;

deploying said pipe lengths;

deploying an electric power source;

telescoping the first extremities of various ones of the pipe lengths into the bell sockets in the second extremities of various others of the pipe lengths to form a pipeline; and

sequentially connecting the power source to the various connection means to heat the corresponding heating coil to a sufficient temperature to rapidly fuse the pipe lengths together and disconnecting the power source when the fusion is substantially complete.

17. A method of constructing a plastic pipeline, the method comprising:

fabricating a plurality of thermoplastic pipe lengths, each pipe length characterized by a predetermined fusion temperature and including a first extremity characterized by a predetermined outside diameter, a second extremity fabricated of high density thermoplastic and having an interior surface defining a bell socket adapted to telescopically receive the first extremity of another of said pipe lengths in close fitting relationship and an indicator recess in an exterior surface of each bell socket the recess having a bottom wall spaced sufficiently close to the interior surface to melt when fusion is substantially complete, a heating coil fabricated of resistance wire coated with medium density thermoplastic and disposed in a gland in the bell socket, and connection means in electrical communication with the heating coil and adapted for rapid connection to an electric power source;

deploying said pipe length;

deploying an electric power source;

telescoping the first extremities of various ones of the pipe lengths into the bell sockets in the second extremities of various others of the pipe lengths to form a pipeline; and

sequentially connecting the power source to the various connection means to heat the corresponding heating coil to a sufficient temperature to melt the medium density thermoplastic, the molted thermoplastic being operative to transfer heat from the heating coil to the exterior surface of the pipe length in the socket and to the interior surface of the socket and thereby to rapidly fuse the pipe lengths together, and disconnecting the power source when the fusion is substantially complete.