Thermal sealing appts. with multi-stage cylinder

The utility model relates to a thermal sealing device with a multi-stage cylinder, which is used for an aluminum-plastic packing machine in medicinal industry. The device is the improvement of the existing thermal sealing device with a single-stage cylinder, namely, the single-stage cylinder of the thermal sealing device with a single-stage cylinder is changed into a multi-stage cylinder, the stage number n of which is 2, 3, 4,... The utility model is composed of a cylinder sleeve (13), an upper end cover (16) and a lower end cover (12) which are arranged on an upper and a lower ports of the cylinder sleeve (13), (n-1) spacing rings (14) which are arranged in the cylinder sleeve (13) and divide the cylinder sleeve (13) into n equal small cylinder sleeves, a mandrel (18) passing through the spacing rings (14) and the lower end cover (12), and n pistons which are arranged on the mandrel (18) and are respectively positioned in the n small cylinder sleeves. The utility model reserves the advantages of the thermal sealing device with a single-stage cylinder, and has the characteristic of good thermal sealing quality for PTP aluminum boxes and PVC plastic sheets.