Belling machine for forming sockets on the ends of pipes made of thermoplastic material and method of forming a socket at the end of a pipe made of thermoplastic material

A belling machine for forming sockets on the ends of pipes made of thermoplastic material, comprising:

• a forming chamber, for the insertion and forming of a socket on the heated end of a pipe made of thermoplastic material on which a socket is to be formed;
• a process air feed line, taking the process air from a compressed air source and introducing the process air into the forming chamber through an inlet;
• cooling means for cooling the end of the pipe comprising a refrigerating machine with an operating cycle operating on a refrigerant, the refrigerating machine being equipped with a closed circuit for recirculating the refrigerant which in turn comprises a refrigerant evaporator located along a path of the process air from the compressed air source to the forming chamber;
• wherein the process air feed line conveys the process air into the evaporator, resulting in transfer of heat from the process air to the refrigerant inside the evaporator, thus cooling the process air;
• said cooling means further comprising a refrigerating section which cools a heat exchange liquid recirculating in a respective closed circuit, the closed circuit of the heat exchange liquid comprising a first heat exchanger, located on the process air feed line upstream of the evaporator relative to the forming chamber along the process air path from the compressed air source to the forming chamber, the process air feed line conveying the process air into the first heat exchanger, resulting in transfer of heat from the process air to the heat exchange liquid and pre-cooling of the process air.