Seal head for tube expansion apparatus

摘要

An apparatus is provided for filling a tube (20) with fluid and for pressurizing the tube (20), in order to expand and form it within a die (22) for example. The apparatus provides a high flow-low pressure fluid circuit for quickly filling and draining the tube, together with a separate high pressure-low flow fluid circuit for pressurizing and depressurizing the tube (20). The high pressure circuit of the apparatus comprises a shaft (1) having a longitudinal bore (4) communicating with a high pressure fluid source and control means, tube sealing means (7) adjacent the forward end of the shaft (1) for sealing the tube (20) when the shaft (1) is engaged with the tube (20) and high pressure fluid flows into the tube (20), and shaft reciprocating means (8) for advancing and retracting the shaft (1). The high flow circuit of the apparatus comprises a forwardly open shroud (19), housing the forward end of the shaft (1) when retracted and having a rearward opening slidably and sealably engaging the forward end of the shaft (1) rearward of the tube sealing means (7), the interior of the shroud (19) communicating with a high flow-low pressure fluid source and control means, external seal means (24) about the forward opening of the shroud (19) for sealing an external surface adjacent an end of the tube (20), and shroud reciprocating means for advancing and retracting the shroud (19). In operation, the shroud (19) is advanced to seal the external surface (23), the tube (20) is filled with low pressure fluid, the shaft (1) is advanced and the tube sealing means (7) engaged, the tube (20) is pressurized, and the process is reversed to release the tube (20).