| 摘要 |
A casing 11 of plastics material has a channel 15 in which a tube 16 is centered, with an annular gap 17 therebetween. A spiral heating element 14 is disposed in the tube 16. Sealing ribs or lips 18 seal the annular gap 17 and serve to centre the tube 16 in the channel 15. The tube 16 is of a heat resistant plastics material. The arrangement and composition of the tube 16 aim to improve insulation, and reduce deposits of impurities. <IMAGE> |
