| 摘要 |
A machine for cutting and sealing bags from a web of thermoplastic sheet material includes low inertia drive rolls to feed the thermoplastic sheet in closely controlled, incremental lengths. The drive rolls are driven by a fluid motor which is controlled by a stepping motor. The sheet is fed to a cutting and sealing head which has means for gripping the fed segment of the web to hold it in position to be cut and sealed. Sealing is effected by resistance wires on the head which are applied to the thermoplastic sheet. The amount of electrical energy applied to the resistance heating wires is controlled and measured carefully to avoid overheating or underheating of the wire.
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