Abstract:
An electrofusion coupling for coupling a first device to a second device, includes a first part having an outer end for coupling to the first device, and an inner end formed with a surface of a curved configuration; and a second part having an end engaging the inner end of the first part and formed with a surface of a complementary curved configuration as the first part. The curved configurations of the two parts is such that the second part may be pivoted to locate its longitudinal axis at different angles with respect to the longitudinal axis of the first part. At least one of the parts is of a thermoplastic material and includes an electrical heater coil embedded along its curved surface for fixing by electrofusion the angular position of the second part with respect to the first part.

Description:
RELATED PATENT APPLICATION 
     This application is a National Phase Application of PCT/IL2004/000137 having International Filing Date of 12 Feb. 2004, which claims the benefit of Israeli Patent Application No. 154578 filed 23 Feb. 2003. The contents of the above Application are all incorporated herein by reference 
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention is related to electrofusion couplings for coupling a first device to a second device. The invention is particularly useful in electrofusion couplings for coupling plastic pipes to other devices, e.g., another plastic pipe, a saddle, a spigot or connector; and the invention is therefore described below particularly with respect to such applications. 
     Plastic pipes for conducting fluids are commonly joined by electrofusion wherein an electrofusion sleeve is applied over the pipe ends to be joined and is electrically energized to heat-fuse or weld the plastic sleeve to the pipe ends. When a plurality of pipe sections are thus joined together by electrofusion to form a continuous line, it is critical that the longitudinal axes of the pipe sections where joined together be perfectly aligned as any deviation from perfect alignment will cause the pipe sections to bend and thereby to produce tension stresses on one side of the bend and compressional stresses on the opposite side of the bend. Such bending stresses, which can result in early rupture of the plastic pipe, are frequently difficult to avoid particularly when joining together short sections of pipe, or when traversing a curve in the pipeline. In such cases, it is frequently necessary to insert specially-dimensioned angular sections or elbows to accommodate bends without introducing stresses in the joined pipe sections. This significantly increases the manufacturing costs, as well as the inventory and maintenance costs, of the pipe line. 
     Similar problems may also be involved where a plastic pipe is to be joined to a saddle, e.g. for receiving another plastic pipe thereacross, or where the plastic pipe is to be joined to a spigot or connector for connection to another device. 
     OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION 
     An object of the present invention is to provide an electrofusion coupling which can be used for accommodating misalignment between pipe sections to be joined by the electrofusion coupling without introducing such stresses in the pipe sections or other devices to be joined. While the invention is particularly useful in an electrofusion coupling for joining a plastic pipe to another plastic pipe, or to another plastic device, it can also be used for coupling other types of devices together by electrofusion in a manner to accommodate misalignment between the two devices while maintaining the integrity of the electrofusion system. 
     According to a broad aspect of the present invention, therefore, there is provided an electrofusion coupling for coupling a first device to a second device, comprising: a first part having an outer end for coupling to the first device, and an inner end formed with a surface of a curved configuration; and a second part having an end engaging the inner end of the first part and formed with a surface of a complementary curved configuration as the first part, the curved configurations of the two parts being such that the second part may be pivoted to locate its longitudinal axis at different angles with respect to the longitudinal axis of the first part; at least one of the parts being of a thermoplastic material and including an electrical heater coil embedded therein along its curved surface for fixing by electrofusion the angular position of the second part with respect to the first part. 
     According to a more specific aspect of the present invention, there is provided an electrofusion coupling for coupling a first device to a second device, comprising: a first part of thermoplastic material having an outer end for coupling the first device, and an inner end formed with a surface of spherical configuration; and a second part also of thermoplastic material having an end engaging the inner end of the first part and formed with a surface of complementary spherical configuration as the first part, the curved configurations of the two parts being such that the second part may be universally pivoted to locate its longitudinal axis in different planes and at different angles with respect to the longitudinal axis of the first part; at least one of the parts including an electrical heater coil embedded therein along the spherical surface thereof for fixing the angular position of the second part with respect to the first part by electrofusion. 
     In the preferred embodiments of the invention described below, the outer end of the first part is formed with a bore of cylindrical configuration, and the first device is a plastic pipe to be received within the bore of the first part and to be fixed therein by electrofusion. 
     In one preferred embodiment of the invention described below, the end of the second part opposite to that receiving the first part is formed with an outer surface of curved configuration, and the coupling further comprises a third part including an outer end for coupling to the second device, and an inner end formed with an inner surface of complementary curved configuration as the outer surface at the opposite end and of the second part so as to be rotatable therein to different angular positions with respect to the second part. In the described preferred embodiment, the third part is also of a thermoplastic material, and the outer end of the third part also includes an electrical heater coil embedded therein for coupling to the second device also by electrofusion. 
     In a second described preferred embodiment, the end of the second part opposite to that received within the first part is of a saddle shape for receiving the second device. 
     In a described third embodiment, the end of the second part opposite to that received within the first part is of tubular shape, e.g., to serve as a spigot or as a connector, for coupling to the second device. 
     In the three preferred embodiments referred to above, the surface of curved configuration of the first part is the inner surface at the inner end of the first part, and the surface of complementary curved configuration of the second part is the outer surface at the end of the second part which is received within the inner curved surface at the inner end of the first part. 
     A fourth embodiment of the invention is also described below, wherein the surface of curved configuration of the first part is the outer surface at the inner end of the first part, and the surface of complementary curved configuration of the second part is the inner surface at the end of the second part which receives the inner curved surface at the inner end of the first part. 
     As will be described more particularly below, an electrofusion coupling constructed in accordance with the foregoing features allows two devices, such as plastic pipes, to be coupled together by electrofusion in a manner which accommodates non-alignment and which permits the two devices to be pivoted to different angles with respect to each other as may be desired for a specific application. 
     Further features and advantages of the invention will be apparent from the description below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
         FIG. 1  illustrates a three-part electrofusion coupling constructed in accordance with the present invention for coupling together two plastic pipes; 
         FIG. 2  is a longitudinal sectional view of the electrofusion coupling of  FIG. 1 ; 
         FIG. 3  illustrates a two-part electrofusion coupling constructed in accordance with the present invention for coupling a plastic pipe to a saddle; 
         FIG. 4  is a longitudinal sectional view of the electrofusion coupling of  FIG. 3 ; 
         FIG. 5  illustrates a two-part electrofusion coupling constructed in accordance with the present invention, for coupling a plastic pipe to a tubular device, such as a spigot or connector to serve as an outlet tap or the like; 
         FIG. 6  is a longitudinal sectional view illustrating the electrofusion coupling of  FIG. 5 ; 
         FIG. 7  is a longitudinal section view illustrating another two-part electrofusion coupling constructed in accordance with the present invention for coupling a plastic pipe to a saddle; 
         FIG. 8  is an enlarged sectional view illustrating one of the parts in the electrofusion coupling of  FIG. 7 ; and 
         FIG. 9  illustrates a modification in the three part electrofusion coupling of  FIGS. 1 and 2 . 
     
    
    
     It is to be understood that the foregoing drawings, and the description below, are provided primarily for purposes of facilitating understanding the conceptual aspects of the invention and various possible embodiments thereof, including what is presently considered to be a preferred embodiment. In the interest of clarity and brevity, no attempt is made to provide more details than necessary to enable one skilled in the art, using routine skill and design, to understand and practice the described invention. It is to be further understood that the embodiments described are for purposes of example only, and that the invention is capable of being embodied in other forms and applications than described herein. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  illustrate a three-part coupling, generally designated  2 , for coupling together two plastic tubes (not shown) such as to permit the longitudinal axes of the two plastic pipes  2  to be located at any desired angle with respect to each other in the same plane, or in different planes, according to the requirements of the specific application. 
     The illustrated electrofusion coupling  2  includes a first part  10  at one end for receiving one of the plastic pipes, and a second part  20  at the opposite end for receiving the second plastic pipe. It further includes a third, intermediate part  30  coupling the two parts  10  and  20  together such as to permit each part to be universally pivoted with respect to the other part to any desired angle within a predetermined range. 
     Thus, part  10  of electrofusion coupling  2  is formed at its outer end with a cylindrical bore  11  for receiving its respective plastic pipe (not shown). Part  10  is further formed with an inner annular shoulder  12  to serve as an abutment for locating the received plastic pipe. The opposite end of part  10  is formed with a concavely-curved inner surface  13  for receiving the respective end of the intermediate part  30  such as to permit parts  10  and  30  to be pivoted to different angular positions with respect to each other, as will be described more particularly below. 
     Part  10  further includes an electrical heater coil  14  at the outer end of the part to receive the plastic pipe, and another electrical heater coil  15  at the opposite end to receive the respective end of the intermediate part  30 . The two electrical coils  14  and  15  are connected in series between two electrical terminals  16  and  17 . In some applications, however, it may be desirable to connect each of the two electrical coils  14 ,  15  to a separate pair of terminals in order to enable them to be energized separately, or together, as desired. 
     Part  20  at the opposite end of the electrofusion coupling  2  is similarly formed with: a cylindrical bore  21  for receiving the other plastic pipe (not shown); an annular shoulder  22  serving as an abutment for the received plastic pipe; an inner concavely-curved surface  23  at the opposite end of the part for receiving the respective end of the intermediate coupling  30 ; an electrical heater coil  24  at the end of the part to receive the plastic pipe; an electrical heater coil  25  at the opposite end of the part to receive the intermediate coupling part  30 ; and a pair of electrical terminals  26  and  27  for energizing the two heater coils  24  and  25 . 
     The intermediate part  30  of the electrofusion coupling  2  is formed with a bore therethrough consisting of a cylindrical section  31  at its center, and two conical sections at its opposite ends  32 ,  33 . The outer surface of the central section  31  is cylindrical, as shown at  34 . The outer surfaces of the two ends  32 ,  33 , are convexly-curved, as shown at  35  and  36 , respectively, with a curvature complementary to that of the concavely-curved inner surfaces  13 ,  23  of the two end parts  10 ,  20 . 
     In the preferred embodiment of the invention illustrated in  FIGS. 1 and 2 , the complementary curved surfaces ( 13  of part  10 , and  35  of part  30  at one end; and  23  of part  20  and  36  of part  30  at the opposite end) are preferably of a spherical configuration so as to allow the two end parts  10 ,  20 , to be universally pivotable with respect to the intermediate part  30  to different angular positions in different planes. It is contemplated, however, that in some applications, it may suffice to pivot the two pipes to be coupled to different angular positions with their longitudinal axes in the same plane, in which case these curved surfaces could be cylindrical, rather than spherical. 
     The manner of using the electrofusion coupling illustrated in  FIGS. 1 and 2  will be apparent from the above description. Thus, one of the pipes to be coupled is inserted within bore  11  of part  10  until its end abuts annular shoulder  12 ; and the other pipe to be coupled is inserted into bore  21  of part  20  until its end abuts shoulder  22 . The two pipes are then pivoted to the desired angle with respect to each other. Electrical coils  14  and  15  are energized via terminals  16  and  17  to electrofuse part  10  with respect to its received plastic pipe and the intermediate part  30 ; and electrical coils  24  and  25  are energized via their respective terminals  26  and  27  to electrofuse part  20  with respect to the second pipe and intermediate part  30  of the electrofusion coupling. 
       FIGS. 3 and 4  illustrate a two-part saddle-type electrofusion coupling for coupling a plastic pipe to a saddle, e.g., for mounting another pipe at right-angles to it as in a T-fitting. One of its two parts, namely, that for receiving one pipe, is the same as part  10  in  FIGS. 1 and 2 , and therefore that part and its components are identified by the same reference numerals. The other part is designed to serve as the saddle, and is generally designated  40  in  FIGS. 3 and 4 . 
     The second part  40  illustrated in  FIGS. 3 and 4  is formed at one end with a construction similar to the respective end of the intermediate part  30  in  FIG. 2 . Thus, part  40  is formed with a bore having a central cylindrical section  41  and an outer conical section  42  corresponding to bore sections  31  and  32  in  FIG. 2 . Part  40  is further formed with an outer surface having a central section  44  of cylindrical configuration and an end section  45  of convexly-spherical configuration, corresponding to outer surface  23  in  FIG. 2 . 
     The opposite end of part  40  of the electrofusion coupling illustrated in  FIGS. 3 and 4  is formed as a curved saddle, as shown at  46 , extending perpendicularly to and communicating with bore section  41  of that part. Saddle section  46  of part  40  includes electrical heater coils  47  and  48  at the opposite sides of bore section  41 , adapted to be energized via a pair of electrical terminals  49 , only one of which is seen in  FIGS. 3 and 4 . 
     The manner of using the electrofusion coupling illustrated in  FIGS. 3 and 4  will be apparent from the above description. Thus, one pipe is inserted into part  10  of the coupling, as described above with respect to  FIGS. 1 and 2 , and the other pipe is applied across the curved saddle  46  of part  40 . Part  40  is then pivoted to the desired angular position with respect to part  10 . Heater coils  14  and  15  are then electrically energized to electrofuse the two parts in the pivoted angular position, and also to electrofuse the plastic pipe within part  10 . Electrical heater coil  47  may then be energized to electrofuse the plastic pipe within the saddle section  46  of part  40 . 
       FIGS. 5 and 6  illustrate a two-part electrofusion coupling in which one part, that for receiving a plastic pipe, is of the same construction as part  10  in  FIGS. 1 ,  2  and  3 ,  4 , respectively; that part and its components are therefore identified by the same reference numerals. The second part, identified as  50  in  FIGS. 5 and 6 , is pivotally mounted at one end to part  10 , and is formed at its opposite end into a tubular configuration for use, for example, as a spigot, connector, or the like, to serve as an outlet (or inlet) for the fluid conducted within the plastic pipe. 
     Thus, as shown in  FIGS. 5 and 6 , part  50  is formed with a bore therethrough having a cylindrical section  51  and a conical section  52  at one end, the latter being formed with an outer surface  55  of convexly spherical configuration, corresponding to spherical surface  45  in  FIG. 4 , for pivotal movement within the concavely-spherical surface  13  of part  10 . Thus, part  50  may be pivoted to any desired position with respect to part  10 , and electrofused in that position by electrically energizing the electrical heater coils  14  and  15  of part  10 , in the same manner as described above. 
       FIGS. 7 and 8  illustrate a two-part saddle-type coupling similar to that of  FIGS. 3 and 4 , except that in this case the spherical surfaces, which permit one part to be pivoted with respect to the other, are reversed in the two parts. Thus, one of the parts, that indicated  110  in  FIGS. 7 and 8 , is of similar construction as part  10  in  FIGS. 3 and 4 , except that the spherical surface, therein designated  113 , is convexly-formed on the outer surface of part  110 , rather than concavely-formed on its inner surface; and the spherical surface engaged thereby by the second part  140  is concavely-formed on its inner surface, as shown at  145 , rather than on its outer surface. In all other respects, the two-part electrofusion coupling illustrated in  FIGS. 7 and 8  may be constructed in the same manner as described above with respect to  FIGS. 3 and 4  with the annular shoulder  112  for locating the plastic pipe to be inserted into part  110 , the heater coils  114 ,  115  for electrofusing the pipe to part  110  and part  110  to part  140 , and heater coil  147  for electrofusing the other pipe to the saddle  146 . 
     It will be appreciated that a similar modification can be made to the electrofusion couplings illustrated in  FIGS. 1 ,  2  and  4 ,  5 , respectively, namely by providing the spherical surface of part  10  on the outer surface of that part, rather than on the inner surface, and by providing the spherical surface of the second part on the inner surface of that part rather than on the outer surface. 
       FIG. 9  illustrates a modification in the three-part coupling of  FIGS. 1 and 2 , particularly in the construction of the third, intermediate part, designated  30  in  FIGS. 1 and 2 , and  130  in  FIG. 9 . Since the first and second parts  10  and  20 , respectively, are of the same construction as in  FIGS. 1 and 2 , these parts and their respective elements are identified in  FIG. 9  by the same reference numerals as in  FIGS. 1 and 2 . 
     The main modification in the  FIG. 9  construction is that, whereas in  FIGS. 1 and 2  the inner and outer ends  32 ,  33  of the third, intermediate part  30  have a common longitudinal axis, the outer ends  132 ,  133  of part  130  in  FIG. 9  have longitudinal axes LAa, LAb, respectively, at an angle to each other. Accordingly, part  130  will also have two central cylindrical sections  131   a ,  131   b  and two outer cylindrical surfaces  134   a ,  134   b , both at the same angle with respect to each other. By thus providing a fixed angular bend in the third, intermediate part  130 , the electrofusion coupling of  FIG. 9  is capable of accommodating larger angular displacements between the two pipes to be coupled together. 
     While the invention has been described with respect to several preferred embodiments, it will be appreciated that many other variations and applications may be made. For example, while the two electrical coils (e.g.,  14 ,  15  shown in  FIG. 2 ) are connected in series to a common pair of terminals (e.g.  16 ,  17 ), they may be connected in parallel, or to a separate pair of terminals. In addition, the two or three parts could be fixed to each other at the desired angular position by electrofusion, while one or both of the coupled devices (e.g., plastic pipes, saddles, etc.) could be fixed to the respective end of the coupling by mechanical means, such as a compressional, split-ring type mechanical couplings, according to the particular application. Many other variations, modifications and applications of the invention will be apparent.