Crown and bridge extractor

摘要

The proposed crown extractor possesses a cylindrical housing 1 whose rear wall comprises an orifice 3 and in which a striker 2 with a central bore is displaceable, a rod 4 extending through the central bore. At the front end of the rod there is a gripping device 5 for the crown to be extracted and at the rear end there is a terminal member 6 covering the orifice 3. The striker 2 is pressed forward by a spring 9 against a housing stop, the rear end of the spring pressing the terminal member on to the orifice 3. The striker 2 subdivides the housing interior into a front chamber 10 connected to a source of compressed air and a rear chamber 12 connected to the front chamber via a flow restriction channel 13. If the gripping device is applied on to the crown to be extracted and the housing 1 is retracted the terminal member 6 lifts off the orifice 3, the pressure in the rear chamber 12 drops quickly and the pressure remaining in the front chamber 10 accelerates the striker 2 rearwards until it impinges on the terminal member 6, and this is transmitted via the rod 4 on to the gripping device 5. <IMAGE>