Methods and devices for the production of a pipe from biaxialy oriented thermoplastic material having an integrated socket

Method according to one or more of the preceding claims, in which use is made of a chamber member or a mould with a first and a second half, which are provided with clamping surfaces which are brought into engagement with the end part at both its axial ends and thus clamp the end part fixedly against the support bush or socket-forming mandrel.

Method according to one or more of the preceding claims, in which the fixed region of the end part in the vicinity of the free end of the pipe is subsequently removed, and in which the other fixed region is preferably not heated or only scarcely heated.

Method for applying an integral socket to a pipe made from biaxially oriented thermoplastic material, which pipe has a pipe body and is provided, at one or both ends, with an integral socket, in which method a pre-fabricated pipe from biaxially oriented thermoplastic material is subjected to a socket-forming operation using a socket-forming device, by means of which an end part, which has been heated to a suitably elevated temperature, of the pipe which has previously been produced is formed into a socket, after which the end part which has been deformed into a socket is cooled, characterized in that the heated end part of the pipe, or an annular region of the said end part, is held in a substantially stationary position at one of its axial ends, and in that the other axial end of the pipe is displaced in the axial direction with respect to the stationary axial end by displacement means associated with the socket-forming device, in such a manner that the end part, or the relevant annular region thereof, is lengthened in the axial direction.

Method according to one or more of the preceding claims, in which use is made of a socket-forming mandrel of the expandable type with substantially radially displaceable or expandable forming elements, for example groove-forming elements for forming a groove on the inner side of the socket, which forming elements can be displaced or expanded between a retracted position and an expanded position.

Method according to claim 28, in which, during the expansion of the forming elements, the end part is internally subjected to a fluid pressure which promotes the expansion of the end part, which internal fluid pressure is eliminated when the forming elements have reached their expanded position, after which the relevant section of the end part is subjected to an external fluid pressure, preferably until the end part has become dimensionally stable through cooling.

Method according to one or more of the preceding claims, in which the pipe which has previously been produced has an end part of a greater wall thickness than the remaining part of the pipe, and in which the axial stretching of the end part prior to the socket-forming operation is preferably greater than or equal to the axial stretching of the remaining part of the pipe.

Method for producing a pipe from biaxially oriented thermoplastic material, which pipe has a pipe body and, at one or both of its ends, an integral socket, a pre-fabricated pipe from biaxially oriented thermoplastic material being subjected to a socket-forming operation using a socket-forming device, which socket-forming device comprises a socket-forming mandrel which is slid into the interior of an end part of the pipe which has previously been produced, which end part, at a suitably elevated temperature, is formed into a socket, after which the end part is cooled and the socket-forming mandrel is removed from the end part, the socket-forming device being provided with force means for generating a force in order to push the pipe onto the socket-forming mandrel, characterized in that the force means are designed to engage on an annular region of the end part of the pipe which adjoins the free edge of the end part, and to push the said annular region over the mandrel, in such a manner that a tensile stress is generated in the end part when the end part is pushed onto the mandrel.

Method for producing a pipe from biaxially oriented thermoplastic material, which pipe has a pipe body and, at one or both of its ends, an integral socket, a pre-fabricated pipe from biaxially oriented thermoplastic material being subjected to a socket-forming operation using a socket-forming device, which socket-forming device comprises a socket-forming mandrel which is slid into the interior of an end part of the pipe which has previously been produced, which end part, at a suitably elevated temperature, is formed into a socket, after which the end part is cooled and the socket-forming mandrel is removed from the end part, characterized in that the end part, prior to the introduction of the socket-forming mandrel, is first heated to a first temperature, which lies, for example, just above the glass transition temperature, and then only an outermost annular region of the end part, which adjoins the free end of the end part, is heated to a second temperature, which is higher than the first temperature, after which the socket-forming mandrel is introduced into the end part, the annular region which is at the second temperature—if the socket-forming mandrel is provided with expandable groove-forming elements—preferably being situated at the location of the groove-forming elements.

Method according to a combination of a plurality of the preceding claims.

Socket-forming device as set forth in one or more of the preceding claims.