runner connecting extruder b not shown in fig2 to channel 67 leading to the reservoir 68 of a second shooting pot 69 equipped with an injection or charging piston 71 here again a spool valve 72 shown in fig2 in the closed position relative to channel 67 controls charging of the reservoir 68 in the closed position of the spool valve 72 the reservoir 68 communicates with the nozzle assembly 64 via channel 70 by virtue of cut out 75 when the spool valve 72 is open the channel 70 is closed link mechanism 85 operates to rotate valve 72 referring to fig3 inverted relative to the position of the nozzle in fig2 note that the nozzle assembly 64 includes a central spigot 73 in thermal contact with manifold block 51 immediately adjacent local heating elements 52 52 as is most apparent in fig2 the spigot 73 fabricated preferably of a good metallic thermal conductor such as beryllium copper is formed with a through channel 74 through which pet flows to the nozzle gate 76 the spigot is supported by minimal bearing surfaces 77 78 in a housing 79 which is spaced from the spigot substantially throughout its length by an insulating air gap 81 this air gap blocks conduction of heat 500 u00b0.