A PIPE JOINT, ESPECIALLY FOR PLASTIC PIPES

Abstract: A pipe joint consists of a socket and a spigot end introduced therein, a sealing ring positioned between the inner surface of the socket and the outer surface of the spigot end for sealing the space between said surfaces, and a locking device (10, 22) for preventing withdrawal of the spigot end from the socket. The locking device comprises one or several locking elements (22) positioned between the inner surface of the socket and the outer surface of the spigot end. The locking elements are adapted to prevent withdrawal of the spigot end from the socket by engaging the outer surface of the spigot end. The locking elements are at their surfaces adapted to engage the outer surface of the spigot end provided with engagement projections and/or the outer surface of the spigoto end is provided with engagement projections adapted to engage the locking elements. The engagement projections constitute a thread which makes it possible to separate the spigot end from the socket by screwing out the spigot end therefrom.

Description: A pipe joint, especially for plastic pipes The present invention relates to a pipe joint, especially a plastic pipe joint, consisting of a socket and a spigot end introduced therein, a sealing ring positioned between the inner surface of the socket and the outer surface of the spigot end for sealing the space between the inner surface of the socket and the outer surface of the spigot end, and a locking device for preventing that the spigot end is withdrawn from the socket. In order to connect plastic pipes with each other there is used a pipe joint consisting of a socket and a spigot end introduced therein, the socket being formed at the end portion of one of the plastic pipes and the jointing is provided by the fact that the end portion of the other pipe forms a spigot end which is introduced into the socket, or by connecting two end portions provided with spigot ends by means of a double socket. Plastic pipes jointed in this way are to a great extent used as water pipelines and sewer lines positioned in the ground and there is at conventional pipe joints of the type described above a large risk that the spigot end shall be displaced out from the socket. This risk is present especially at pipe bends, at the connection with manholes and at branch points in the pipeline. Because thereof it is according to official stipulations necessary at such points to provide the pipe joints with some kind of locking device preventing the spigot end from being displaced out from the socket. Such a locking device can for example be constituted by a so called anchorage shackle which, however, has the drawback of being constituted by a heavy and expensive construction consisting of cast iron. Attempts have been made to replace this anchorage shackle by means of a locking device comprising an annular surface having a conical ly narrowing diameter in the direction of withdrawal of the spigot end and one or several locking elements positioned between this surface and the outer surface of the spigot end. These locking elements are at the displacement of the spigot end in the direction of withdrawal from the socket because of their engage- ment with the conically narrowing surface forced against the outer surface of the spigot end into a rigid engagement therewith so as to prevent withdrawal of the spigot end from the socket. A drawback of previously known locking devices of this kind is the problem of separating the spigot end from the socket when the pipeline is damaged in such a way that it is necessary to replace parts of the pipeline. The object of the present invention is to provide a plastic pipe joint having a locking device of the type last mentioned in which said drawbacks are not present In order to comply with this object the locking elements are at their surfaces adapted to engage the outer surface of the spigot end and/or the spigot end is at its outer surface adapted to engage the locking elements provided with engagement projections, the pipe joint being characterized in that the engagement projections constitute a thread which makes it possible to separate the spigot end from the socket by screwing out the spigot end therefrom Another drawback of previously locking devices of said kind is the fact that the locking devices subject the socket and the spigot end to great forces which in many cases lead to a breaking of the socket and/or the spigot end In order to prevent this drawback the pipe joint according to the invention is in a preferred embodiment provided with stop surfaces for restricting the displacement of the locking elements in the direction for withdrawal of the spigot end from the socket and thereby for restricting the forcing of the locking element against the conically narrowing surface and the outer surface of the spigot end In a pipe joint of this kind the forces acting on the socket and the spigot end by means of the locking element are restricted in such a way that these forces can not cause breaking of the socket or the spigot end In order to provide a correct function of the locking device it is suitable that the pipe joint includes spring element for forcing the locking element in the direction of withdrawal of the spigot end so that the locking elements are subse- queπtly to the introduction of the spigot end into the socket displaced into engagement position with the outer surface with the spigot end under the influence of the spring elements In a preferred embodiment of the invention the sealing ring and the locking elements are connected with each other and positioned in an inner groove in the socket, the bottom of the groove being constituted by the annular surface having a conically narrowing diameter in the withdrawal direction of the spigot end, the stop surface for restricting the displacement of the locking element in the withdrawal direction and the engagement surface for the spring elements being constituted by opposite side surfaces of the groove The invention shall be described in the following with reference to the accompanying drawings Fig 1 is an axial section of a double socket and the ends of two plastic pipes which shall be connected with the socket so as to constitute a pipe joint according to the invention Fig 2 is a plan view of a sealing ring included in the pipe joint according to the invention, the sealing ring having locking elements connected therewith Fig 3 shows a section of the socket of Fig 1 during the introduction of a pipe end portion therein Fig 4 shows a part of the socket corresponding to Fig 3 and the pipe end portion introduced therein for constituting a pipe joint according to the invention Fig 5 shows the pipe joint according to the invention at an attempt to withdraw the pipe end portion from the socket Fig 6 is an axial section corresponding to Fig 1 of a double socket and the ends of two plastic pipes for constituting a modified embodiment of a pipe joint according to the invention In Fig 1 there is shown an axial section of a double socket 2 consisting of plastic material for connecting two plastic pipes, the spigot ends 4 and 6 of these plastic pipes being shown in axial section outside the socket 2 before the introduction of the spigot ends therein Subsequently to the introduction of the spigot ends 4 and 6 into the socket 2 there is established two pipe joints according to the invention The socket 2 has two annular, inwardly open, inner grooves 8 each having an annular bottom surface 10 having conically narrowing diameter in the direction of the ad- jacent free end of the socket 2 and two side surfaces 12 and 14, the side surface 2 being positioned adjacent the free end of the socket 2 The socket 2 has also a central stop bead 15 constituting stop surfaces for restπct- ing the introduction of the spigot ends 4 and 6 into the socket 2 In each groove 8 there is positioned a sealing ring 16 consisting of rubber-elastic material having a sealing lip 18 extending obliquely inwards and a spring element 20 formed as a lip obliquely directed towards the side surface 14 of the groove 18, the spring element engaging the side surface 14 of the groove 8, which constitutes an engagement surface for the spring element 20, this engagement providing that the sealing ring 16 and the locking elements supported thereby and consisting of hard metal preferably metal are displaced against the opposite side surface 12 of the groove 8 The side surface 12 constitute a stop surface for restricting the dispiace- ment of the ring consisting of the sealing ring 16 and the locking elements 22 against the narrowing section of the conical surface 10 constituting the bottom of the groove 8 As appears from Fig 2, the number of locking elements 22 is six and there is be- tween the end portions of the locking elements 22 sections 24 consisting of rubber- elastic material which is unitary with the rubber-elastic material of the sealing ring 16 The elastic connection of the sealing elements 22 by means of the elements 24 provides that the ring consisting of the sealing ring 16 and the locking elements 22 can be compressed in the groove 8 from a non-influenced condition by being dis- placed from the deeper against the lower part of the groove 8 along the conical surface 10 However, this reduction of the ring consisting of the sealing ring 16 and the locking elements 22 is restricted by the engagement of the locking elements 22 with the stop surface constituted by the side surface 12 of the groove 8 At their inner surfaces the locking elements 22 have peripherally extending projections 26 having triangular sections and having heights of for example 0 4 mm which elements form engagement projections adapted to engage the outer surface of the spigot ends 4 and 6 so as to lock the spigot ends in relation to the socket 2 In accordance with the invention the projections 26 constitute a thread which makes it possible to separate the spigot ends 4 and 6 connected with the socket 2 from the socket by screwing out the spigot ends 4 and 6 from the position in the socket When the spigot ends 4 and 6 are introduced into the socket, the rings consisting of the sealing rings 16 and the locking elements 22 will, as appears from Fig 3, be displaced in the direction of introduction of the spigot ends 4 and 6 against the side walls 14 of the groove 8 against the action of the spring elements 20 This displacement of the rings provides that the rings are allowed to increase their diameters as the rings are displaced against the part of the conical surfaces 10 having a larger diameter This facilitates the introduction of the spigot ends 4 and 6 into the socket When the spigot ends 4 and 6 have been introduced into the socket to the position in which the end surfaces of the spigot ends engage the stop bead 16 and the inwardly displacement of the spigot ends 4 and 6 is thereby completed, the spring elements 20 act for displacing the rings consisting of the sealing πngs 16 and the locking elements 22 from the side surfaces 14 of the groove towards the side surfaces 12, the diameter of the rings being thereby reduced because of the displacement in the direction for the narrowing dimensions of the surfaces 10 The rings will be displaced in said direction until the locking elements 22 by means of their en- gagement projections 26 firmly engage the outer surfaces of the spigot ends 4 and 6, wherein the position according to Fig 4 can for example be established The positions of the rings consisting of the sealing rings 16 and the locking elements 22 in the grooves 8 are of course dependent on the relationship between the diameters of the elements included in the pipe joints, i e the socket, the rings and the spigot ends, but it is desirable that the ring consisting of the sealing ring 16 and the locking elements 22 shall in the axial direction thereby be positioned in the middle of the groove At an attempt to withdraw the spigot ends 4 and 6 from the socket 2 the locking ele- ments 22 and therewith the sealing rings 16 connected with the locking elements are displaced by the spigot end towards the free ends of the socket, i e towards the conically narrowing parts of the surfaces 10 This provides for an increased pressure of the locking elements 22 outwardly against the wall of the socket defining the groove 8 as well as inwardly against the outer surface of the spigot ends 4 and 6 When the locking elements 22 reach their positions in which they engage the stop surface 12 a continuing withdrawal of the spigot ends 4 and 6 from the socket is prevented which provides also that continuing withdrawal or influence on the spigot ends 4 and 6 in a direction for withdrawal from the socket does not provide for such increased influences on the socket and the spigot ends that would provide for breakage of the socket 2 and/or of the spigot ends 4 and 6 This position is shown in Fig 5 in which the locking elements 22 engage the stop surface 12 In the position shown in Fig 5 in which the engagement projections 26 of the locking elements 22 have been forced into the outer surfaces of the spigot ends 4 and 6 the engagement projections have in the outer surface of the spigot ends 4 and 6 provided a wave- shaped deformation of the outer surface in correspondence to the engagement projections When the pipeline is damaged in which the pipe joint according to the invention is included, it can sometimes be desirable to separate the spigot ends from the socket for changing the pipes in which the spigot ends are included This can in the pipe joint according to the invention be provided in a simple way by cutting the pipeline in which the spigot end is included whereupon the part of the pipeline on which the spigot end is provided can in a simple be screwed out from the socket by using the thread constituted by the engagement projections 26 Because thereof there is not required any replacement of the socket which has been required in prior art pipe joints of the kind in which the spigot end is by means of locking elements fixed in relation to the socket Fig 6 shows an axial section corresponding to Fig 1 of a double socket 2 and the ends of two plastic pipes 4 and 6 for constituting a modified embodiment of a pipe joint according to the invention In the embodiment according to Fig 6 the socket 2 is designed in exactly the same way as the socket 2 in the embodiment according to Fig 1 and is because thereof provided with the same reference numerals as the socket shown in Fig 1 As in the embodiment according to Fig 1 there is in each groove 8 of the socket according to Fig 6 positioned a sealing ring 28 having an obliquely inwardly directed sealing lip 30 and an axially extending, peripherally outer spring element 32 The embodiment of the sealing ring 28 shown in Fig 6 facilitates the manufacturing of the sealing ring in relation to the sealing ring shown in Figs 1 - - 5. Thus, it is necessary to manufacture the sealing ring 16 by means of extrusion and jointing while the sealing ring 28 of the type shown in Fig. 6 can be manufactured by means of injection moulding or compression moulding without any requirement for jointing. The spring elements 32 of the sealing rings 28 according to Fig. 6 engage with the side surfaces 14 of the groove 8 in the same way as the sealing rings 16 according to the embodiment of Fig. 1 and have with regard to the spring " elements 32 the same function as the sealing rings 16 according to Figs. 1 - 5. Also in the embodiment according to Fig. 6 the pipe joint according to the invention includes locking elements 34 of substantially the same design as the locking elements 22 in the embodiment according to Figs. 1 - 5. However, the locking elements 34 consist of a hard rubber material, such as a rubber material having a Shore hardness of 60 - 90 and preferably 80, and the locking elements 34 lack engagement projections at their inner surfaces. Such engagement projections 36 are instead provided at the outer surface of the spigot ends 4 and 6 and because of the fact that the locking elements 34 engage with this engagement projections 36 there is provided a locking of the spigot ends 4 and 6 in the socket 2 in the same way as in the embodiment according to Figs. 1 - 5. The engagement projections 36 are designed as a thread on each spigot end which, as described above with reference to the em- bodiment according to Figs. 1 - 5, can be used for screwing out the spigot ends 4 and 6 from the socket for example when the pipes including the spigot ends are damaged. With regard to the function there is substantially complete agreement between the embodiment according to Figs. 1 - 5 and the embodiment according to Fig. 6, while the embodiment according to Fig. 6 can be considered to constitute certain advantages from the manufacturing point of view. The invention can be modified within the scope of the following claims.

Claims: CLAIMS 1 A pipe joint consisting of a socket (2) and a spigot end (4, 6) introduced therein, a sealing ring (16, 28) positioned between the inner surface of the socket and the outer surface of the spigot end for sealing the space between the inner surface of the socket and the outer surface of the spigot end, and a locking device (10, 22, 34) for preventing withdrawal of the spigot end from the socket, the locking device comprising one or several locking elements (22, 34) positioned between the inner surface of the socket and the outer surface of the spigot end and adapted to prevent withdrawal of the spigot end from the socket by engaging the outer surface of the spigot end, the locking elements (22) being at their surfaces adapted to engage the outer surface of the spigot end provided with engagement projections (26) and/or the outer surface of the spigot end (4, 6) being provided with engagement projections (36) adapted to engage the locking elements (28), characterized in that the engagement projections (26, 36) constitute a thread which makes it possible to separate the spigot end (4, 6) from the socket by screwing out the spigot end therefrom 2 A pipe joint as claimed in claim 1, characterized in that the locking device comprises an annular surface conically narrowing in the direction of withdrawal of the spigot end and that the locking elements (22, 34) positioned between this surface and the outer surface of the spigot end at displacement of the spigot end in the direction of withdrawal from the socket by engagement with the conically narrowing surface are forced against the outer surface of the spigot end (4, 6) into a firm engagement therewith 3 A pipe joint as claimed in claim 2, characterized in that the socket (2) is provided with stop surfaces (12) for restricting the displacement of the locking elements (22, 34) in the direction of withdrawal of the spigot end and thereby for re- stπcting the forcing of the locking elements against the conically narrowing surface (10) and against the outer surface of the spigot end 4 A pipe joint as claimed in claim 2 or 3, characterized by a sprig element (20, 32) for forcing the locking elements (22, 34) in the withdrawal direction of the spigot end and thereby into engagement with the conically narrowing surface (10) and the outer surface of the spigot end. 5. A pipe joint as claimed in any of the preceding claims, characterized in that the sealing ring (16; 28) and the locking elements (22; 34) are contacting each other and are positioned adjacent each other in the axial direction of the pipe- joint. 6. A pipe joint as claimed in claim 4 and 5, characterized in that the spring element (20; 32) is positioned on the sealing ring (16; 28) at the opposite side of the sealing ring in relation to the locking elements (22; 34) and by spring action engages an engagement surface (14) provided at the inner surface of the socket. 7. A pipe joint as claimed in claim 5 and 6, characte rized in that the sealing ring (16; 28) and the locking elements (22; 34) are positioned in an inner groove (8) in the socket (2). 8. A pipe joint as claimed in claim 7, characterized in that the bottom of the groove (8) is provided by the annular surface conically narrowing in the direction of withdrawal of the spigot end (4; 6) and that the stop surfaces (12) for restricting the displacement of the locking element in the direction of withdrawal and the engagement surface (14) for the spring element (20; 32) are constituted by opposite side surfaces of the groove (8). 9. A pipe joint as claimed in any of the preceding claims, characterized in that the locking elements (22; 28) are present in a number of two or several locking elements which together form an annular element having distances between the end surfaces of the locking elements. 10. A pipe joint as claimed in claim 9, characterized in that the locking elements (22; 28) are bound to the sealing ring (16). 11. A pipe joint as claimed in any of the preceding claims, characterized in that the pipe joint is included in a double socket (2) for connecting two spigot ends (4; 6) with each other.

Inventors: GUSTAFSSON LEIF, SPORRE STEN, GUSTAFSSON, LEIF, SPORRE, STEN
Applicants: ENEBACKEN SKREA AB, GUSTAFSSON LEIF, SPORRE STEN, GUSTAFSSON, LEIF, SPORRE, STEN
Application year: 1998
Main classification: F16L21
IPC codes: F16L37