Method and apparatus for joint resin pipes using high-frequency electric induction heating

• US 5,466,916 A
• Filed: 07/25/1994
• Issued: 11/14/1995
• Est. Priority Date: 09/24/1993
• Status: Expired due to Fees

• Current Assignee: Hidec Co., Ltd.
• Original Assignee: Asahi Yukizai Kogyo Company Limited, Hidec Co., Ltd.
• Inventors: Yamashita, Takehiro, Matsuoka, Koichi, Akabane, Atsushi, Iguchi, Atsushi
• Primary Examiner(s): Leung, Philip H.
• Application Number:
  US08/279,797
• Time in Patent Office: 477 Days
• Field of Search: 219/633, 219/634, 219/611, 219/643, 285/21, 156/272.4, 156/274.2, 264/26, 264/27, 264/25
• US Class Current: 219/633
• CPC Class Codes: B29C 37/0082 Mechanical anchoring B29C66/303 takes precedence
• CPC Class Codes: B29C 65/18 using heated tools
• CPC Class Codes: B29C 65/3644 being a ribbon, band or strip
• CPC Class Codes: B29C 65/3648 said strip being perforated
• CPC Class Codes: B29C 65/3668 characterised by the means for supplying heat to said heated elements which remain in the join, e.g. special induction coils
• CPC Class Codes: B29C 65/3676 being metallic
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• CPC Class Codes: B29C 66/1142 Single butt to butt joints
• CPC Class Codes: B29C 66/1312 Single flange to flange joints, the parts to be joined being rigid the parts to be joined being flexible B29C66/133
• CPC Class Codes: B29C 66/30341 non-integral with the parts to be joined, e.g. making use of extra elements B29C65/562 takes precedence
• CPC Class Codes: B29C 66/324 Avoiding burr formation
• CPC Class Codes: B29C 66/3242 on the inside of a tubular or hollow article
• 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 66/5229 involving the use of a socket
• CPC Class Codes: B29C 66/52298 said socket being composed by several elements
• CPC Class Codes: B29C 66/612 Making circumferential joints
• CPC Class Codes: B29C 66/636 using a support which remains in the joined object
• 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 66/73161 Roughness or rugosity
• CPC Class Codes: B29C 66/91313 by measuring the voltage, i.e. the electric potential difference or electric tension
• CPC Class Codes: B29C 66/91315 : by measuring the current intensity
• 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 66/91443 : following a temperature-time profile B29C65/38 takes precedence
• CPC Class Codes: B29C 66/91651 : by controlling or regulating the heat generated by Joule heating or induction heating
• 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 66/91921 : in explicit relation to another temperature, e.g. to the softening temperature or softening point, to the thermal degradation temperature or to the ambient temperature
• CPC Class Codes: B29C 66/91931 : in explicit relation to the fusion temperature or melting point of the material of one of the parts to be joined
• CPC Class Codes: B29C 66/91951 : in explicit relation to time, e.g. temperature-time diagrams
• 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 2023/12 : PP, i.e. polypropylene
• CPC Class Codes: B29K 2027/06 : PVC, i.e. polyvinylchloride
• CPC Class Codes: B29K 2027/12 : containing fluorine
• CPC Class Codes: B29K 2027/16 : PVDF, i.e. polyvinylidene fluoride
• CPC Class Codes: B29K 2027/18 : PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29K 2071/00 : Use of polyethers , e.g. PEEK, i.e. polyether-etherketone or PEK, i.e. polyetherketone or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2081/04 : Polysulfides, e.g. PPS, i.e. polyphenylene sulfide or derivatives thereof
• CPC Class Codes: B29L 2023/22 : Tubes or pipes, i.e. rigid bent tubes not for use as pipe couplings B29L2023/004
• CPC Class Codes: H05B 6/105 : using a susceptor

Abstract

When resin pipes are connected through induction heating, the resin pipes of this invention do not form inside bulges due to air and resin expansion during the heating process. A cylindrical heater made of stainless steel is placed around the joint between two resin pipes made of polyvinylidene fluoride. The heater is then heated by induction heating to weld the joint of resin pipes. The heater has a plurality of holes on the cylindrical surface so that air and molten resin located between the heater and the resin pipes are released through the holes.

Claims

1. A method of connecting resin pipes, comprising the steps of:

(a) contacting two resin pipes positioned end to end to be connected to form an area of contact,

(b) disposing a cylindrical metallic heater along the contact area between said resin pipes, wherein at least one material of said heater is selected from the group consisting of stainless steel, brass, and aluminum, and said heater has an axial length of from about 1/4 to 2/3 of a nominal diameter of said resin pipes,

(c) surrounding said heater with a coil, connecting a resonance capacitor and a secondary winding of an output transformer serially between both terminals of said coil, connecting a primary winding of another output transformer to an inverter which converts direct electric power from a power source into alternating electric power with a predetermined voltage and frequency, and connecting said inverter to said power source,

wherein said heater is excited by high-frequency electric current heating said heater by induction heating and said joint between said resin pipes is welded together,

(d) exciting said heater by high-frequency electric current, heating said heater by induction heating, wherein said contact between said resin pipes is welded together, and simultaneously said cylindrical metallic heater is fixed to the outer surface of said resin pipes.

2. A method of connecting resin pipes as claimed in claim 1, wherein said heater comprise a plurality of holes disposed in a cylindrical surface in the direction of thickness.

3. A method of connecting resin pipes as claimed in claim 2, wherein a diameter of each of said plurality of holes disposed in said cylindrical surface ranges from 0.1 mm to 5 mm.

4. A method of connecting resin pipes as claimed in claim 2, wherein said plurality of holes are disposed in several rows, and each of said holes in each of said rows are disposed at equal intervals.

5. A method of connecting resin pipes as claimed in claims 1 or 2, wherein an inside diameter of said heater has a dimensional tolerance larger than an outside diameter of said resin pipes, and said heater is heated in close vicinity to said resin pipes.

6. A method of connecting resin pipes as claimed in claim 1 or 2, wherein said heater has a cylindrical shape formed by welding ends of a plate together.

7. A method of connecting resin pipes as claimed in claim 4, wherein said plate is made of stainless steel.

8. A method of connecting resin pipes as claimed in claims 1 or 2, wherein cylindrical stoppers comprising a material with heat-resisting and electrical insulating properties are attached around said resin pipes on both sides of said heater.

9. A method of connecting resin pipes as claimed in claim 8, wherein a material for said cylindrical stoppers is from the group consisting of phenolic resin, epoxy resin, unsaturated polyester resin, and diallyl phthalate resin.

10. A method of connecting resin pipes as claimed in claim 1 or 2, wherein said cylindrical metallic heater is disposed around each resin pipe in a state that space exists resin pipes which ranges from 0.1 to 10 mm.

11. An apparatus for connecting resin pipes, said apparatus comprising:

a cylindrical metallic heater disposed around a contact area between two resin pipes to be connected end to end, wherein said heater comprises at least one material selected from the group consisting of stainless steel, brass, and aluminum, and said heater has an axial length of from about 1/4 to 2/3 of a nominal diameter of said resin pipes,

a coil surrounding said heater, and

a resonance capacitor and a secondary winding of an output transformer which are connected serially between both terminals of said coil,

a primary winding of another output transformer which is connected to an inverter converting direct electric power from a power source into alternating electric power with a predetermined voltage and frequency, wherein said inverter and said power source are connected to each other,

a high-frequency electric current generator for exciting high-frequency electric current into said coil to heat said heater by induction heating, wherein said contact area between said resin pipes is welded together, and for simultaneously fixing said metallic heater to the outer surface of said resin pipes.

12. An apparatus for connecting resin pipes as claimed in claim 11, wherein said heater further comprises plurality of holes disposed in a cylindrical metal plate in a direction of thickness of said plate.

13. An apparatus for connecting resin pipes as claimed in claim 12, wherein said plurality of holes are disposed in several rows, and each of said holes in each of said rows are disposed at equal intervals.

14. An apparatus for connecting resin pipes as claimed in claim 12, wherein said plate is made of stainless steel.

15. An apparatus for connecting resin pipes as claimed in claims 13 or 14, wherein an inside diameter of said heater has a dimensional tolerance larger than an outside diameter of said resin pipes, and said heater is heated in close vicinity to said resin pipes.

16. An apparatus for connecting resin pipes as claimed in claim 13, wherein said heater has a cylindrical shape formed by welding ends of a plate together.

17. An apparatus for connecting resin pipes as claimed in claim 16, wherein a diameter of each of said plurality of holes disposed in said cylindrical surface ranges from 0.1 mm to 5 mm.

18. An apparatus for connecting resin pipes as claimed in claims 11 or 12, wherein cylindrical stoppers comprising a material with heat-resisting and electrical insulating properties are attached around said resin pipes on both sides of said heater.

19. An apparatus for connecting resin pipes as claimed in claim 18, wherein a material for said cylindrical stoppers is from the group consisting of phenolic resin, epoxy resin, unsaturated polyester resin, and diallyl phthalate resin.

20. An apparatus for connecting resin pipes as claimed in claim 11 or 12, wherein a cylindrical metallic heater is disposed around each resin pipe in a state that space exists between said resin pipes which ranges from 0.1 mm to 10 mm.