WO1997010944A1 - Electrofusion method and device - Google Patents

Electrofusion method and device

Info

Publication number
WO1997010944A1
WO1997010944A1 PCT/IL1996/000113 IL9600113W WO9710944A1 WO 1997010944 A1 WO1997010944 A1 WO 1997010944A1 IL 9600113 W IL9600113 W IL 9600113W WO 9710944 A1 WO9710944 A1 WO 9710944A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
pipe
sleeve
material
electrofusion
coil
Prior art date
Application number
PCT/IL1996/000113
Other languages
French (fr)
Inventor
Oded Katz
Original Assignee
Plasson Maagan Michael Industries Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3404Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the type of heated elements which remain in the joint
    • B29C65/342Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the type of heated elements which remain in the joint comprising at least a single wire, e.g. in the form of a winding
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3472Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint
    • B29C65/3476Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint being metallic
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/01General aspects dealing with the joint area or with the area to be joined
    • B29C66/05Particular design of joint configurations
    • B29C66/10Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/12Joint cross-sections combining only two joint-segments; Tongue and groove joints; Tenon and mortise joints; Stepped joint cross-sections
    • B29C66/122Joint cross-sections combining only two joint-segments, i.e. one of the parts to be joined comprising only two joint-segments in the joint cross-section
    • B29C66/1222Joint cross-sections combining only two joint-segments, i.e. one of the parts to be joined comprising only two joint-segments in the joint cross-section comprising at least a lapped joint-segment
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/01General aspects dealing with the joint area or with the area to be joined
    • B29C66/05Particular design of joint configurations
    • B29C66/10Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/12Joint cross-sections combining only two joint-segments; Tongue and groove joints; Tenon and mortise joints; Stepped joint cross-sections
    • B29C66/122Joint cross-sections combining only two joint-segments, i.e. one of the parts to be joined comprising only two joint-segments in the joint cross-section
    • B29C66/1224Joint cross-sections combining only two joint-segments, i.e. one of the parts to be joined comprising only two joint-segments in the joint cross-section comprising at least a butt joint-segment
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/50General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
    • B29C66/51Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
    • B29C66/52Joining tubular articles, bars or profiled elements
    • B29C66/522Joining tubular articles
    • B29C66/5221Joining tubular articles for forming coaxial connections, i.e. the tubular articles to be joined forming a zero angle relative to each other
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/50General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
    • B29C66/51Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
    • B29C66/52Joining tubular articles, bars or profiled elements
    • B29C66/522Joining tubular articles
    • B29C66/5229Joining tubular articles involving the use of a socket
    • B29C66/52291Joining tubular articles involving the use of a socket said socket comprising a stop
    • B29C66/52292Joining tubular articles involving the use of a socket said socket comprising a stop said stop being internal
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/71General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
    • B29C66/712General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined the composition of one of the parts to be joined being different from the composition of the other part
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/73General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/735General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the extensive physical properties of the parts to be joined
    • B29C66/7352Thickness, e.g. very thin
    • B29C66/73521Thickness, e.g. very thin of different thickness, i.e. the thickness of one of the parts to be joined being different from the thickness of the other part
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/74Joining plastics material to non-plastics material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3468Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the means for supplying heat to said heated elements which remain in the join, e.g. special electrical connectors of windings
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3472Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint
    • B29C65/3476Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint being metallic
    • B29C65/348Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint being metallic with a polymer coating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/71General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00General aspects of processes or apparatus for joining preformed parts
    • B29C66/70General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/74Joining plastics material to non-plastics material
    • B29C66/742Joining plastics material to non-plastics material to metals or their alloys
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS
    • B29K2023/00Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04Polymers of ethylene
    • B29K2023/06PE, i.e. polyethylene
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS
    • B29K2023/00Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04Polymers of ethylene
    • B29K2023/08Use of copolymers of ethylene as moulding material
    • B29K2023/083EVA, i.e. ethylene vinyl acetate copolymer
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS
    • B29K2077/00Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof as moulding material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29KINDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS
    • B29K2705/00Use of metals, their alloys or their compounds, for preformed parts, e.g. for inserts
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL
    • B29LINDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2023/00Tubular articles
    • B29L2023/22Tubes or pipes, i.e. rigid

Abstract

A method of joining a first pipe (P1) of a plastic material to a second pipe (P2) of a material which does not bond well to the plastic material, utilizes an electrofusion sleeve (2) of a plastic material which bonds well to the plastic material of the first pipe and having a first coil (6) of electrical heater wire on the inner surface at one end of the sleeve to receive the first pipe (P1) and a second coil (7) of electrical heater wire on the inner surface at the opposite end of the sleeve to receive the second pipe (P2). The opposite end of the sleeve includes a bonding material capable of producing a good bond, when activated by heat, between the materials of the sleeve (2) and of the second pipe (P2). The two pipes are inserted into the two ends of the sleeve, and electrical current is applied to the two coils to cause the first end of the sleeve to bond by electrofusion to the first pipe (P1), and the second end of the sleeve to bond by electrofusion and by the bonding material to the second pipe (P2).

Description

ELECTROFUSION METHOD AND DEVICE The present invention relates to a method and device to join together two or more pipes by electrofusion.

Electrofusion is a technique for joining two pipes together by means of sleeves having coils of electrical heater wire such that the two pipes to be joined are inserted into the opposite ends of the sleeve, and then electrical current is applied to the coils to fuse the outer surfaces of the two pipes to the sleeve. This technique is widely used to join together pipes made of the same plastic material, or of plastic materials which bond well to each other by heat. In such cases, the electrofusion sleeve is made of the same material as the plastic pipes, or of a material which bonds well to that of the plastic pipes by electrofusion.

There are applications, however, where it is necessary to join a pipe of a plastic material which does not bond well to a pipe of another material, plastic or metal. For example, polyolefins, e.g., polyethylene, polypropylene and polybutylene, are very difficult to bond to many other materials, such as nylons (polyamides) and polyvinychloride, and therefore the electrofusion technique has not generally been used in such applications. As a result, mechanical coupling devices are generally used for pipes of polyethylene or of other materials which do not bond well to other plastics or to metal. An object of the present invention is to provide an electrofusion method and device for joining a pipe made of a plastic material which generally does not bond well to pipes of other plastics or of metal.

According to one aspect of the present invention, there is provided a method of joining a first pipe of a plastic material to a second pipe of a material which does not bond well to the plastic material, comprising: providing an electrofusion sleeve of a plastic material which bonds well to the plastic material of the first pipe, the electrofusion sleeve having a first coil of electrical heater wire on the inner surface at one end of the sleeve to receive the first pipe and a second coil of electrical heater wire on the inner surface at the opposite end of the sleeve to receive the second pipe; providing an bonding material at the opposite end of the sleeve so as to be in direct contact with the plastic material of the sleeve and with the material of the second pipe when received in the opposite end of the sleeve, the bonding material being one capable of producing a good bond, when activated by heat, between the materials of the sleeve and of the second pipe; inserting the first pipe into the first end of the electrofusion sleeve, and the second pipe into the opposite end of the electrofusion sleeve; and applying electrical current to the first and second coils to cause the first end of the sleeve to bond by electrofusion to the first pipe, and the second end of the sleeve to bond by electrofusion and by the bonding material to the second pipe.

According to further features in one described preferred embodiment, the bonding material is provided in the form of a layer, preferably a coating, on the electrical heater wire of the second coil; and in a second described embodiment, it is provided as a preformed film over the second coil to contact the second pipe when inserted into the opposite end of the sleeve.

Preferred examples of the materials that can be used for the two pipes are a polyolefin, preferably polyethylene, for the plastic material of the first pipe, and a nylon (polyamide) for the material of the second pipe. In such an application, the electrofusion sleeve would also be made of polyethylene. The invention, however, could also be used with plastic pipes of other materials that do not bond well to each other, e.g., with polypropylene for the first pipe and/or another polar material for the second pipe.

The thermoplastic bonding material is preferably a polyolefin based copolymer containing active polar groups which, upon application of heat energy, develop a free radical which then forms a bond with any polar group or polar material in contact with it. One such material is PE (polyethylene) copolymer with maleic anhydride

0

II o

W "■*-* r_ which is derived from maleic acid minus H_0, Another is EVA with maleic anhydride. Commercial formulations of such materials are known.

The invention also provides a device for joining by electrofusion pipes of a plastic material which does not bond well to other plastic materials or to metals.

Further features and advantages of the invention will be apparent from the description below.

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

Fig. 1 is a longitudinal half-sectional view illustrating one form of electrofusion sleeve constructed in accordance with the present invention;

Fig. 2 is an enlarged fragmentary view illustrating the construction of the first coil of electrical heater wire at one end of the electrofusion sleeve of Fig. 1 ;

Fig. 3 is an enlarged fragmentary view illustrating the construction of the second coil of electrical heater wire at the opposite end of the electrofusion sleeve; and Fig. 4 illustrates a modification in the construction of the second coil of electrical heater wire of Fig. 3.

The electrofusion fitting illustrated in Fig. 1 comprises an electrofusion sleeve 2 of a thermoplastic material formed with a socket 3 at one end for receiving a first plastic pipe P- , and a socket 4 at the opposite end for receiving a second pipe P- to be joined to the first pipe by electrofusion. The two sockets 3, 4, are preferably separated by an annular shoulder 5 (or other projection) to limit the insertion of the two pipes into their respective sockets with the two pipes coaxially aligned with each other and with the electrofusion sleeve.

The electrofusion sleeve 2 includes a first coil 6 of electrical heater wire on the inner surface at one end of the sleeve to receive pipe P.. when inserted into socket 3, and a second coil 7 (preferably a section of coil 6) of electrical heater wire on the inner surface at the opposite end of the sleeve to receive pipe P- when inserted into socket 4. Sleeve 2 further includes electrical terminals 8, 9 for applying electrical heating current to coils 6, 7, to melt the inner surfaces of the sleeve, and the outer surfaces of the plastic pipes received therein, and thereby to bond them together by electrofusion.

The construction and manner of using electrofusion fittings, insofar as described above, are well known for bonding together pipes made of the same plastic material, or - 6 -

of plastic materials which are easily bondable together by electrofusion. However, this technique is not generally used for joining plastic pipes which are not easily bondable together by electrofusion, such as joining a pipe of a polyolefin (e.g., polyethylene) with a pipe of another material not easily bondable to polyethylene, such as nylon (polyamide) or other polar plastic, or metal. The electrofusion fitting illustrated in Fig. 1 , particularly as further described with respect to Figs. 2-4, is especially constructed to enable bonding together by electrofusion pipes made of one material, e.g., polyethylene, with another material, e.g., a polar plastic or a metal, not normally bondable to polyethylene.

In the example described below, it will be assumed that pipe P1 received within socket 3 is made of polyethylene, and P_ received in socket 4 is made of another plastic material, such as a nylon (polyamide), normally not directly bondable to the material of pipe P...

In this example, the electrofusion sleeve 2 is also made of polyethylene. The electrical heater wire of coil 6 is also coated with polyethylene, as shown by coating 6a in Fig. 2. Thus, when electrical current is applied to coil 6, its polyethylene coating 6a melts in the fusion zone Z1 , and similarly the adjacent surfaces of the sleeve 2 and the pipe within socket 3, also melt in this zone to produce an integral bond between the polyethylene of sleeve 2, of wire coating 6a, and of the polyethylene in the plastic pipe P1 received in socket 3. Zones Z_ and 7*-. on opposite sides of zone Z1 are colder zones in which fusion generally does not take place.

However, since pipe P- is of a material not normally bondable to polyethylene (being polyamide in this example), coil 7 enclosing socket 4 in the opposite side of sleeve 2 to receive pipe P->, is not constructed in exactly the same manner as coil 6. Thus, as shown in Fig. 3, the electrical heater wire of coil 7 includes an outer layer 7a, preferably in the form of a coating, of an bonding material which, when activated by the heat generated in coil 7, is capable of producing a good bond between the polyethylene of sleeve 2 , and the polyamide of pipe P2- Particularly good results have been obtained when the outer coating 7a is a polyolefin based copolymer containing active polar groups which, upon application of heat energy, develop a free radical which then forms a bond with any polar group or polar material in contact with it. One such material is PE

(polyethylene) copolymer with maleic anhydride

0

which is derived from maleic acid minus H_0. Another is EVA ethylene vinyl acetate with maleic anhydride.

When the electrical current is applied to coil 7, its outer coating 7a is activated to produce a firm bond between the polyethylene of sleeve 2 and the polyamide of pipe P2 in the fusion zone underlying coil 7, corresponding to zone Z1 underlying coil 6 at the end of the sleeve receiving pipe P...

The foregoing technique also better assures a firm bond to the coating 7a and the coil wire 7, thereby decreasing or eliminating the possibility of the occurrence of a leak path between the coating and the wire, which can be especially dangerous in gaseous fuel applications.

Fig. 4 illustrates a variation wherein the bonding material, capable of producing a good bond between the polyethylene of the fitting and the material (e.g., polyamide) of plastic pipe P2, is provided as a preformed film over coil 7 to contact pipe P_ when inserted into socket 4.

Thus, as shown in the fragmentary view of Fig. 4, the electrofusion sleeve 12 is also made of polyethylene as described above, but in this case the electrical heater wire of coil 17, at the end of the sleeve formed with socket 4 to receive pipe P2, is also coated with polyethylene 17a (rather than with the bonding material), and the bonding material is applied as a preformed film 17b for the whole stretch of coil 17. Film 17b of the bonding material thus serves as an interface between the polyethylene coating 17a and the plastic of pipe P-. When electrical current is applied to coil 17, the polyethylene coating 17a melts so as to become integrally bonded to the polyethylene of the sleeve 12; and the bonding material of the preformed film 17b becomes heat-activated to produce a good bond between the polyethylene coating 17a and the adjacent surface of the polyamide plastic pipe P_.

It will be appreciated that in the variation of Fig. 4, the construction of the electrofusion sleeve 12, and of the coil at the opposite end of the sleeve to receive the plastic pipe P.. , are otherwise the same as described above.

The good bond between the wire and the pipe, as described above with respect to Figs. 3 and 4, also substantially reduces the possibility of a leakage path occurring along the wire between it and the plastic pipe, which can be especially dangerous with respect to plastic pipes conducting pressurized gaseous fuel.

While the invention has been described with respect to two preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many other variations, modifications and applications of the invention may be made.

Claims

1. A method of joining a first pipe of a plastic material to a second pipe of a material which does not bond well to said plastic material, comprising: providing an electrofusion sleeve of a plastic material which bonds well to the plastic material of said first pipe, said electrofusion sleeve having a first coil of electrical heater wire on the inner surface at one end of the sleeve to receive said first pipe and a second coil of electrical heater wire on the inner surface at the opposite end of the sleeve to receive said second pipe; providing an bonding material at said opposite end of the sleeve so as to be in direct contact with said plastic material of the sleeve and with said material of the second pipe when received in said opposite end of the sleeve, said bonding material being one capable of producing a good bond, when activated by heat, between the materials of said sleeve and of said second pipe; inserting said first pipe into said first end of the electrofusion sleeve, and said second pipe into said opposite end of the electrofusion sleeve; and applying electrical current to said first and second coils to cause said first end of the sleeve to bond by electrofusion to said first pipe, and said second end of the sleeve to bond by electrofusion and by said bonding material to said second pipe.
2. The method according to Claim 1 , wherein said second pipe is also of a plastic material.
3. The method according to either of Claims 1 or 2, wherein said bonding material is in the form of a layer on the electrical heater wire of said second coil.
4. The method according to Claim 3, wherein said bonding material is coated over the electrical heater wire of said second coil.
5. The method according to Claim 2, wherein said bonding material is a preformed film over said second coil in contact said second pipe when inserted into said opposite end of the sleeve.
6. The method according to any one of Claims 1-5, wherein said first plastic material is a polyolefin.
7. The method according to Claim 6, wherein said first plastic material is polyethylene.
8. The method according to either of Claims 6 or 7, wherein said bonding material is a polyolefin based copolymer containing active polar groups which, upon application of heat, develop free radicals forming bonds with polar groups of the polyolefin in contact with the bonding material.
9. The method according to Claim 8, wherein said bonding material is a polyethylene copolymer which includes maleic anhydride as the active ingredient.
10. The method according to any one of Claims 1-9, wherein said electrofusion sleeve is made, and said first coil of electrical heater wire is coated, with the same plastic material as said first pipe.
11. A device for joining a first pipe of a plastic material to a second pipe of a material which does not bond well to said plastic material, comprising: an electrofusion sleeve made of a plastic material which bonds well to the plastic material of said first pipe, said electrofusion sleeve having a first coil of electrical heater wire on the inner surface at one end of the sleeve to receive said first pipe and a second coil of electrical heater wire on the inner surface at the opposite end of the sleeve to receive said second pipe; an bonding material at said opposite end of the sleeve located to be in direct contact with said plastic material of the sleeve and with said material of the second pipe when received in said opposite end of the sleeve, said bonding material being one capable of producing a good bond, when activated by heat, between the materials of said sleeve and of said second pipe; and terminals for applying electrical current to said first and second coils to cause said first end of the sleeve to bond by electrofusion to said first pipe, and said second end of the sleeve to bond by electrofusion and by said bonding material to said second pipe.
12. The device according to Claim 11, wherein said bonding material is a thermoplastic material.
13. The device according to Claim 12, wherein said bonding material is in the form of a layer on the electrical heater wire of said second coil.
14. The device according to Claim 13, wherein said bonding material is coated over the electrical heater wire of said second coil.
15. The device according to Claim 12, wherein said bonding material is a preformed film over said second coil to contact said second pipe when inserted into said opposite end of the sleeve.
16. The device according to any one of Claims 11-15, wherein said first plastic material is polyolefin, and said bonding material is a polyolefin based copolymer with active polar groups which, upon application of heat, develop free radicals forming bonds with polar groups of the polyolefin in contact with the bonding material.
17. The device according to Claim 16, wherein said bonding material is a polyethylene copolymer which includes maleic anhydride as the active ingredient.
18. The method according to any one of Claims 11-17, wherein said electrofusion sleeve is made, and said first coil of electrical heater wire is coated, with the same plastic material as said first pipe.
PCT/IL1996/000113 1995-09-20 1996-09-18 Electrofusion method and device WO1997010944A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
IL115364 1995-09-20
IL11536495 1995-09-20

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP19960930342 EP0851807A1 (en) 1995-09-20 1996-09-18 Electrofusion method and device
US09039225 US6127662A (en) 1995-09-20 1998-03-16 Electrofusion method and device

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US09039225 Division US6127662A (en) 1995-09-20 1998-03-16 Electrofusion method and device

Publications (1)

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WO1997010944A1 true true WO1997010944A1 (en) 1997-03-27

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Application Number Title Priority Date Filing Date
PCT/IL1996/000113 WO1997010944A1 (en) 1995-09-20 1996-09-18 Electrofusion method and device

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EP (1) EP0851807A1 (en)
CN (1) CN1061293C (en)
WO (1) WO1997010944A1 (en)

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Also Published As

Publication number Publication date Type
CN1201416A (en) 1998-12-09 application
EP0851807A1 (en) 1998-07-08 application
CN1061293C (en) 2001-01-31 grant

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