| 摘要 |
The valve has a thermoplastic valve body 12 moulded around a subassembly including a sleeve 26 and a rotatable valve disc 16 comprising a pair of opposed disc halves secured to a stem 18 which is mounted for rotation within the sleeve. The valve body 12 includes a central flow passage bounded by the sleeve, and disc and stem are rotatably mounted in the flow passage for movement between an open position and a closed position in which a sealing ring 54 around the periphery of the disc seats on the inside of the sleeve to shut off flow through the flow passage. The butterfly valve is made by securing the disc halves on opposite sides of the stem within the sleeve, with the sealing ring interposed between the disc halves, positioning the resulting subassembly in a mould having a cavity arranged to define the valve body and a pair of cores which engage the disc, and injecting molten thermoplastic material into the mould cavity. <IMAGE> |
