| 摘要 |
754,936. Electric resistance heaters. PFAFF AKT.-GES., G. M. Jan. 19, 1954 [Jan. 19, 1953], No. 1527/54. Class 39(3). [Also in Group VIII] In apparatus for continuously seam-welding synthetic thermoplastic sheet materials 8, 9 between pressure feed rollers 11, 12, a resistance heating band 13 is located in front of each roller on a stationary carrier 30, 31 of insulating material and has a part lying close to the materials 8, 9 before they pass between the rollers. The heating arrangement is shown in connection with the top roller only ; one end of band 13 is connected by. a stirrup 35 to a contact 32, while the other end passes through a slit in a supporting steel band 34 which connects it to a second contact 33, a strip 36 of mica being inserted between bands 13 and 34. Each band 13 is connected, through contacts 32, 33, to its own heating circuit having a variable resistance and measuring instruments. The bands 13 are adapted to slide resiliently on protective strips 15, 16, e.g. of cellulose foil, which cover the sheets 8, 9 to be welded. |
