Lifting structure of engraving machine

A lifting structure of an engraving machine, the engraving machine including a lifting platform having pivot holes each corresponding in position to a screw rod, each of the pivot holes being provided with a screw seat for engagement of the screw rod;

• the lifting platform further having a connecting hole, the connecting hole being mounted with a rotatable shaft seat, a drive gear being provided below the shaft seat, a sprocket being provided below the screw seat, a driven gear being provided below the sprocket to mesh with the drive gear, the sprockets of the pivot holes being connected by a chain;
• the screw seat including an upper screw sleeve, a lower screw sleeve, an upper thrust bearing, a lower thrust bearing, and a spring, a top end of the upper screw sleeve being provided with a disc portion, the disk portion having at least two perforations and a central upper screw hole;
• the lower screw sleeve being rotatable in the pivot hole through the upper thrust bearing and the lower thrust bearing, a top end of the lower screw sleeve having a head portion, the head portion having two positioning screw holes corresponding in position to the perforations and a central lower screw hole, the spring being located between the upper screw sleeve and the lower screw sleeve, two screws passing through the perforations and being screwed to the positioning screw holes respectively, the upper screw sleeve being spaced from the lower screw sleeve;
• an outer wall of the lower screw sleeve being provided with an outer threaded portion, a bottom of the lower screw sleeve being coaxially connected with the sprocket;
• a disc spring being provided below the sprocket, the threaded portion being screwedly connected with a thread ring.