Abstract:
A tapping tee assembly ( 10 ) comprises an integrally moulded saddle ( 12 ), body ( 14 ) and socket ( 16 ). The tapping tee assembly can be mounted on a pipeline thereby enabling a cutter to travel through the body of the fitting in order to cut a hole in the pipeline. The saddle ( 12 ) is provided with a saddle-shaped electrofusion element mat ( 18 ) and the socket ( 16 ), which is integral with the body ( 14 ) and in fluid connection with the axial bore ( 20 ) of the body, is provided with a second electrofusion element ( 22 ). The electrofusion elements ( 22,30 ) are connected by an integrated anvil-shaped connector ( 26 ) and connecting pin ( 28 ) such that both electrofusion elements ( 22,30 ) can be energised simultaneously using two electrical terminals ( 24,38 ), and the device can be manufactured with relative ease.

Description:
[0001]    This invention relates to an arrangement of an electrofusion tapping tee assembly employed to connect a branch service pipe to a mains pipe, and in particular to a method of construction thereof to provide for connection between the two or more electrofusion elements of the assembly. 
       BACKGROUND 
       [0002]    A tapping tee is a fitting that can be mounted on a pipeline thereby enabling a branch connection of the main pipe to be made. Typically, tapping tees comprise a body with a through bore, a saddle that contours the main pipe, and a socket through which a branch pipe can be connected to allow the flow of a fluid from the main pipeline to the branch pipe. A cutter is provided to travel through the body of the fitting and cut the mains pipe once the assembly is connected thereto. The saddle and socket can contain electrofusion elements (or other components incorporating an electrofusion element such as an electrofusion element mat), that are embedded in fusible polymer material to facilitate the bonding of the tapping tee to the main and branch pipes. In this case, the socket is not a socket but a socket. Tapping tees provided with saddles and saddle-shaped electrofusion elements and mats are disclosed in U.S. Pat. Nos. 4,933,037, 4,806,181, 5,104,468, 5,601,315, and 5,348,045, and in UK patent application 2310264. 
         [0003]    EP-A-1674780 discloses a tapping tee assembly for a plastics pipeline, comprising an integrated saddle, body and socket wherein two electrofusion elements, (one a saddle element for connection of the assembly to the main pipe and the other a coil for connection of the socket to a branch pipe), are permanently and directly connected by a conducting material allowing both elements to be energised simultaneously. The manufacture of such a device can be somewhat difficult however, due to problems associated with implanting the metallic connector within the wall of the body during the moulding process. Indeed, the aforementioned specification also suggests in one embodiment employing the cutter itself as a temporary means of connecting the two elements. However, that proposal suffers the potential problem that a specific order of events must take place during assembly of the joint, and in particular that the cutter is driven to a precise location before electrofusion is effected. 
         [0004]    It is an object of the present invention to provide a means whereby construction of a permanent internal connection of the two electrofusion elements can relatively straightforwardly be effected. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0005]    In accordance with the present invention there is provided a moulded tapping tee assembly for a plastics pipeline comprising:
       a saddle, provided with a saddle-shaped saddle electrofusion element having a first terminal at an external end thereof;   a hollow body, integral with the saddle and provided with an axial bore;   a tubular socket, which:
           i) is integral with the hollow body;   ii) has a socket bore in fluid connection with the axial bore of the body;   iii) has an internal surface formed by a mould core that is withdrawn along a socket axis of the socket; and   iv) has a tubular socket electrofusion element having a second terminal at a distal end thereof; and   
           an electrically conductive element, which element connects an internal end of the saddle electrofusion element to a proximal end of the socket electrofusion element,   characterised in that   an internal part of said electrically conductive element is incorporated into the body of the tapping tee during moulding and an exposed part extends from said internal surface, in which said exposed part is shaped so as to fit inside a slot of said mould core, wherein said exposed part is held by said slot transverse to socket axis but remains axially free so that it can be released from said slot subsequent to moulding.       
 
         [0016]    In one preferred embodiment of a tapping tee assembly according to the invention, said exposed part of the electrically conductive element comprises a dovetail section which slots into a corresponding slot of said mould core. Said section may be indented, for example if it comprises a casting. 
         [0017]    Preferably, the first and second electrical terminals of the saddle and socket electrofusion elements are mounted on the saddle and socket respectively, and whereby a source of electrical power can be connected to both electrofusion elements simultaneously. 
         [0018]    In another preferred embodiment, the electrically conductive element comprises two components. Preferably, one component is an anvil comprising said internal and exposed parts and the other component is a connecting pin inserted in a pin-bore of the tapping tee, after moulding thereof, to complete electrical connection between said anvil and said saddle electrofusion element. Preferably, said anvil comprises an eye to receive said pin, wherein the eye of the anvil is preferably conical in shape to guide insertion of said pin. The connecting pin preferably comprises a base, body and head section, where preferably the head of the connecting pin is ridged, said ridges being deformed on engagement of the head in the eye so as to ensure secure electrical bridging between the pin and anvil and retention of the pin therein. Preferably, the head of the connector has a smaller diameter than the body of the connector pin and the base of the connecting pin has a greater diameter than the body of the connecting pin. 
         [0019]    The saddle electrofusion element is preferably a spirally wound electrofusion resistance wire and is preferably integrated with the saddle by over-moulding the saddle, or embedded within the pre-moulded body of the saddle by “ploughing-in” an electrical resistance wire. It is preferred that a separate electrofusion mat forming the saddle electrofusion element is mounted in the saddle or clipped into a recess moulded in the saddle. Preferably, the electrofusion mat comprises a disc of fusible polymeric material, preferably polyethylene, having an electrofusion element embedded therein. Preferably the electrofusion element has parts on both sides of said disc, whereby the mat is fused to both the saddle and the pipeline during electrofusion. The mat preferably has an aperture to coincide with the axial bore of the body. 
         [0020]    Said resistance wire preferably commences at said first terminal, spirals to said internal end on one side of said disc where it passes through an aperture in said disc to the other side thereof, and spirals outwardly back to said first terminal, said electrically conductive element contacting said wire at said aperture. In this event, two elements disposed in parallel with respect to one another form the saddle electrofusion element. Preferably, said pin passes through said aperture contacting the resistance wire therein, where it is preferable that said base has a flange that clamps the internal end of the mat to the saddle, said external end being fixed by said first terminal. Said pin therefore serves two purposes in that it provides an electrical bridge between the electrofusion elements of the saddle and socket and acts as a fastening device fixing the internal end of the mat to the saddle. Preferably, the body of the tapping tee assembly is moulded integrally with the saddle, preferably from polyethylene. 
         [0021]    It is preferred that the electrically conductive element has such low resistance that it does not produce significant heat when an appropriate electrofusion current is passed through it; and/or that the saddle and socket electrofusion elements are balanced such that when the circuit is energised the heat output per unit area per unit time from each of the first and second electrofusion elements is correct in each case “Significant heat” here means sufficient to melt the plastic material surrounding the electrically conductive element. Similarly, it is preferred that said saddle and socket electrofusion elements are balanced such that when the circuit is energised the time taken to complete the fusion bond for each of the first and second fusion elements is substantially identical further enhancing the process efficiency for the user. 
         [0022]    Preferably, the body of the tapping tee assembly is provided with a threaded bore cooperating with external threads on a cutter such that when the cutter is rotated it can travel along the bore to cut a hole in the pipeline when the tapping tee has been connected thereto. 
         [0023]    The socket electrofusion element may be a helically wound electrical resistance wire. Furthermore, it is preferred that said electrically conductive element has a square section post on which said wire is wound. 
         [0024]    In another aspect, the present invention provides a method of constructing said tapping tee described above, which method comprises:
       i) locating said exposed part of said electrically conductive element in said slot of the mould core;   ii) connecting resistance wire to said electrically conductive element and winding same around the mould core;   iii) temporarily attaching via a shearable coupling said second terminal to the mould core and connecting said resistance wire thereto;   iv) closing a mould around said mould core;   v) injecting molten plastics material into the mould and cooling;   vi) separating the mould and withdrawing said mould core in the direction of said socket axis:
           to leave said exposed part of the electrically conductive element in the tapping tee exposed on the internal surface of the socket;   to shear said coupling to leave said second terminal mounted in said socket; and   to leave said resistance wire embedded in said internal surface of the socket; and   
           vii) connecting said saddle electrofusion element to said electrically conductive element.       
 
         [0035]    It is preferred that step vii) comprises inserting said pin in a pin-bore moulded in said body that is coincident with said eye of the anvil. It is further preferred that step vii) connects the saddle electrofusion element to the saddle. 
         [0036]    Preferably, step ii) comprises winding said wire around a square-section post of said electrically conductive element and step iii) includes winding said wire around a square-section length of said second terminal thereby providing a secure fastening. It is then preferred that said wire is tensioned between its connections to the electrically conductive element and second terminal. 
         [0037]    In another aspect, the present invention provides a method of making a moulded tapping tee assembly for a plastics pipeline comprising the steps of:
       providing a mould comprising shell moulds to form external surfaces of a saddle, body and socket of the tapping tee, a body mould core to form an axial bore in a body of the tapping tee and a socket mould core to form a socket bore, said socket mould core being shaped to abut said body mould core in a socket axis direction whereby said socket bore of the tapping tee when formed communicates with said axial body bore;   fitting an exposed part of an electrically conductive element in a slot in the end of the socket mould core, which slot and element are shaped to secure said element in a direction transverse to said socket axis but permit withdrawal of said socket mould core from said element by relative movement between them in a direction parallel said socket axis;   fitting a terminal in a transverse bore of the socket mould core;   connecting an electrical resistance wire to one of said terminal and electrically conductive element and winding said wire around the socket mould core and connecting to the other of said terminal and electrically conductive element;   closing the mould, injecting molten plastics material into the mould and allowing the material to cool before opening the mould and withdrawing said cores from the moulded tapping tee; and   connecting a saddle electrofusion element to said electrically conductive element.       
 
         [0044]    Preferably, said step of connecting a saddle electrofusion fitting comprises mating an electrically conductive pin with an eye of said electrically conductive element, which eye is shielded by a pin-core of said mould during injection of said plastics material, said pin-core being of such diameter that said pin is a close sliding fit in the bore formed by said pin-core in the tapping tee. 
         [0045]    Said pin-core may be arranged parallel said body mould core. Said saddle electrofusion element may be formed separately and may be fitted to said tapping tee and secured thereto at least partially by said pin. 
         [0046]    Said step of connecting an electrical resistance wire comprises winding the wire around a polygonal section part of said terminal and electrically conductive element. The wire may be tensioned between said terminal and electrically conductive element, whereby said tension both retains the wire in connection with said terminal and electrically conductive element and retains the electrically conductive element in position in said slot. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0047]    Embodiments of the invention are further described hereinafter, by way of example, with reference to the accompanying drawings, in which: 
           [0048]      FIG. 1  shows a schematic section through an embodiment of a tapping tee assembly according to the invention; 
           [0049]      FIG. 2  shows a isometric view of a saddle electrofusion mat and element employed in the tapping tee of  FIG. 1 ; 
           [0050]      FIG. 3  shows an exploded view of the tapping tee assembly of  FIG. 1 , complete with saddle electrofusion mat of  FIG. 2 ; 
           [0051]      FIG. 4  illustrates a connecting pin; 
           [0052]      FIG. 5  shows a isometric view of a dovetailed anvil forming an electrically conductive element; 
           [0053]      FIG. 6  shows a terminal of the tapping tee; 
           [0054]      FIG. 7  shows a schematic of a mould socket core with socket electrofusion element, electrical stud terminal and dovetailed anvil fitted thereon prior to moulding the tapping tee of  FIG. 1 ; 
           [0055]      FIG. 8  is a plan view of the moulding core of  FIG. 7 , with the socket electrofusion element removed; 
           [0056]      FIG. 9  is a sectional view of the electrical terminal stud disposed in the socket wall and the mould socket core; 
           [0057]      FIG. 10  is an illustration of the circuit means connecting the saddle electrofusion element to the socket electrofusion element; 
           [0058]      FIG. 11  is a perspective view of the tapping tee showing both terminals; 
           [0059]      FIG. 12  is a sectional top view of the tapping tee assembly along the line C-C in  FIG. 11 ; and 
           [0060]      FIG. 13  is a sectional side view of the tapping tee along the line B-B in  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION 
       [0061]    Referring to the embodiment disclosed in  FIG. 1 , a tapping tee assembly  10  comprises an integrally moulded saddle  12 , body  14  and socket  16 . The saddle  12  is provided with a saddle-shaped electrofusion element mat  18 , which is attached thereto by over-moulding, snap-fit, screws or other fastening means (not shown). The body  14  has an axially extended screw threaded bore  20 , and disposed within the bore, a metal cutter  15  (see  FIG. 3 ) having a screw threaded outer surface that cooperates with the screw thread of the bore. The socket  16  is adapted to receive a branch pipe or spigot (not shown) and is provided with an internal tubular socket electrofusion element  22 . 
         [0062]      FIG. 2  is a detailed illustration of the saddle-shaped electrofusion mat  18 . An electrofusion element, in the form of an electrical resistance wire  30 , is embedded in a spiral track formed on either side of a saddle-shaped fusible polymer material surrounding central aperture  35 , adapted to coincide with the bore  20 . The mat  18  is provided with a hole  32  adjacent the aperture  35  and through which the electrofusion element  30  passes from one side of said polymer material to the other. The ends  37  of the wire  30  are led to another hole  33  adjacent the outside rim of the mat  18 . 
         [0063]      FIG. 3  illustrates how the electrofusion mat  18  fits to the saddle  12  of the tapping tee  10 . The electrofusion element  30  is wound around a first terminal stud  38  that passes through the hole  33  at the external end of said electrofusion mat  18 . The first terminal stud  38  acts to fix the external end of the electrofusion mat  18  to the saddle  12 . 
         [0064]    Returning to  FIG. 1 , socket electrofusion element  22  further comprises two electrical connectors in the form of a second electrical stud terminal  24  and a dovetailed anvil  26 . The electrical stud  24  and dovetailed anvil  26  are connected to opposite ends of the socket electrofusion element  22 , which is wound as a coil in the internal surface of the socket  16 . The electrical stud terminal  24  is surrounded by an upstanding boss  27  forming a socket to receive the plug of an electrical connector of a power source. Said dovetailed anvil  26  electrically connects the two electrofusion elements  30 , 22  via an intermediate connecting pin  28 . 
         [0065]    A detailed illustration of said connecting pin  28  is disclosed in  FIG. 4  and shows it comprising a base  28   a , body  28   b  and head  28   c  sections. Said base  28   a  comprises a flange that acts to clamp the internal end of the electrofusion mat  18  to the saddle  12 . 
         [0066]      FIG. 5  is a detailed illustration of said dovetailed anvil  26  which has an exposed part comprising a dovetail section  42  and an internal part comprising a front post  40  and an arm  44  which has an eye  46  at its end. Said post  40  extends perpendicularly from the plane formed by the base  75  of said dovetail  42 , while said arm  44  extends both perpendicularly and parallel to the plane formed by the base  75  of said dovetail  42 . Indeed, when in position in the tapping tee  10 , the section  44  is circumferential with respect to the longitudinal axis  50  of the body bore  20 . The post  40  and arm  44  are separated by a gap  48 . Said gap allows said socket electrofusion element  22  to be wrapped around the post  40  thus making its connection thereto. Said eye  46  penetrates said arm  44  and is conical in shape to guide the connecting pin  28 . 
         [0067]      FIG. 6  is an illustration of said electrical stud or terminal pin  24  and comprises a cylindrical section  50 , a cubic section  52 , a weak point  54 , and a plug  56 . 
         [0068]    Manufacture of the tapping tee assembly  10  requires injection moulding of a polymer material within a rigid mould that will not deform under temperatures around the melting point of said polymer material. Since the present invention comprises hollow tubes, a pair of moulding cores must be used within the main mould. The mould is not shown but comprises two or more shell moulds that form the external profile of the tapping tee  10 , together with the core moulds, whereby a hollow product of relatively uniform wall thickness is formed. 
         [0069]    Referring now to  FIGS. 7 ,  8  and  9 , there is shown one such moulding core  58  that is used to form the cavity and associated features of the socket  16  during manufacture. The moulding core  58  comprises a hollow tube that will fit into the main mould whereby the space in between will be equal to the desired thickness of the wall of socket  16 . Said moulding core  58  comprises a transverse hole  60  into which the plug end  56  of the electrical stud  24  is driven prior to assembly of the mould (not shown). A slot  62  is formed at one end  63  of the core and in which the dovetail  42  of the dovetailed anvil  26  is disposed. A continuous helical groove  64  is formed around the circumference of the core  58  and in which the socket electrofusion element  22  is disposed. To complete assembly of the moulding core  58 , an electrical resistance wire  22  is first wound around cubic section  52  of the stud  24 , wound under tension around the groove  64 , which retains the wire in position and prevents it from short-circuiting itself by making lateral contact with adjacent turns thereof, and then wound around post  40  of the anvil  26 . The tension in the wire serves several purposes. The first is to keep the wire in the groove  64 . The second is to bite the edges of the cubic section  52  and post  40  into the wire so that good electrical connection is made between them. The third is to ensure, together with the resilience of the wire, that the wire does not come off the stud or post. Finally, the tension retains the anvil  26  in the slot  62 . 
         [0070]    Once the socket core mould is assembled, the entire mould can be assembled, where another mould core (body mould core, not shown, but having a profile matching the bore  20  of the body  14 ) is arranged perpendicularly to axis  100  (end  63  is curved to abut the body core mould with no gap between them). Shell moulds surround the core moulds and molten plastics material is injected between. Once the plastics material has solidified, the mould is opened and the cores withdrawn along the axes  50 , 100 . In withdrawing the socket core  58 , weak point  54  is sheared and fails, leaving plug  56  inside hole  60  (to be dislodged when a new plug is inserted) while the moulded socket retains the remainder of the stud terminal  24 . The cylindrical section  50  then protrudes radially outwards from said socket  16 . The winding of the wire  22  around the cubic section  52  is within the plastics of the wall of the socket and this further serves to retain the winding on the stud  24 . The wire has to stretch to spring out of the groove  64 . 
         [0071]    The anvil  26  slides out of the slot  62 , leaving the post  40  and arm  44  embedded in the plastics material, again, with the winding around the post retained by the plastics of the tapping tee. The dovetail section  42  protruding from the wall within the socket  16 . In a similar manner, the socket electrofusion element  22  is then embedded along the inside of the socket  16  wall.  FIG. 9  shows the stud terminal  24  embedded in the newly formed socket wall  16  prior to said mould core  58  being removed. 
         [0072]    It should be noted that for the purpose of clarity, said weak point  54  has been exaggerated in  FIG. 7 , as has the thickness of the wire  22 . 
         [0073]    The grooves  64  of said moulding core  58  are shallow to reduce the friction between said moulding core  58 , said socket electrofusion element  22  and the socket  16  wall when removing said moulding core  58  from said socket  16 . 
         [0074]    The component of the main mould that produces the saddle  12  component of the tapping tee assembly  10  comprises a core-pin (not shown) that forms a tunnel bore  66  extending upwards from the saddle  12 , through the wall of body  14  parallel the main bore  20 . Said element also prevents said eye  46  of said dovetailed anvil  26  from filling with polymer material during moulding. With said saddle-shaped electrofusion mat  18  fixed in place to said saddle  12 , the hole  32  through said saddle-shaped electrofusion mat  18  is in line with the saddle end of said tunnel  66 . The electrical connecting pin  28  can then be disposed in the tunnel  66  forming an electrical bridge between said saddle electrofusion element  30  of said saddle-shaped electrofusion mat  18  and said eye  46  of said dovetailed anvil  26 . The circuit is disclosed in further detail in  FIG. 10 . 
         [0075]      FIG. 11  gives a perspective view of the tapping tee assembly  10  showing the arrangement of the upstanding terminal bosses  27 , 39  while  FIG. 12  further illustrates the circuit means in particular the arrangement of said anvil  26  within said socket  16  and body  14  walls. The precise location of said anvil eye  46  is also disclosed in  FIG. 12  and is incident with the head section  28   c  of said connecting pin (see  FIG. 13 ). 
         [0076]    Said saddle electrofusion element  30  and socket electrofusion element  22  are composed of a conducting material that produces sufficient heat to melt said fusible polymer material when an electrical current is passed through it, but does not itself, melt or break. Said dovetailed anvil  26 , electrical stud  24  and electrical connecting pin  28  are composed of a good electrically conducting material that does not produce significant heat when an electric current is passed through it. 
         [0077]    The circuit of the tapping tee assembly  10  comprises the upper and lower components of the electrofusion element  30  embedded in the saddle-shaped electrofusion mat  18  connected in parallel with one another, and in series with the socket electrofusion element  22  of the socket  16 . 
         [0078]    While the electrically conductive element that connects the saddle and socket electrofusion elements  30 , 22  is described above as two elements, the anvil  26  and pin  28 , they could be a single component. In that event, pin-part  28  would have to include a stud end  29  (see  FIG. 1 ) protruding from the bottom of the saddle  12  and on which the mat  18  could be located. This stud end  29  would therefore have to engage in a close fitting bore in the shell mould requiring accurate positioning of the socket core  58  with respect to the shell mould. This, together with the long distance between the connection of the dovetail  42  in the slot  62  and the stud end  29 , would make this arrangement less preferable. Furthermore, the pin  28 , when it is separate and is inserted afterwards and has the construction shown in  FIG. 4 , it can serve to retain the mat  18  in place, as well as contacting the wire  30  as it passes through the hole  32  in the mat  18 . Although, this arrangement requires a core-pin to form the tunnel  66  and the core-pin has to engage precisely with the eye  46  of the arm  44 , nevertheless the precision required is not so great since the cantilever of the element  26  is much less. 
         [0079]    Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other moieties, additives, components, integers or steps. 
         [0080]    Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. 
         [0081]    Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. 
         [0082]    The reader&#39;s attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. 
         [0083]    All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
         [0084]    Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
         [0085]    The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.