Abstract: Herein disclosed is a pantagraph type jack in which one of the support portions for supporting an actuating bolt forms a bolt-receiving nut. This bolt-receiving nut is equipped with a dump nut which is composed of a tapered bore and nut segments, and an actuating member which is composed of an actuating ring and a sleeve formed with openings, so that the turning operation of the actuating bolt can be omitted.

Abstract: A device for removing a dump nut from a bolt. The dump nut consists of a casing having an upwardly diverging through-bore, a plurality of separated nut segments slidably inserted in the through-bore in the casing to define a threaded bore therein, and a spring inserted in the through-bore in the casing to constantly urge the nut segments in the downward direction. A bolt is inserted through the threaded bore defined by the nut segments. The nut removing device according to the invention consists of two cross-sectionally arcuate complementary members which are oscillatably joined together at their adjacent side edges. In order to remove the nut from the bolt, the nut is turned in an untightening direction to a small extent, and the nut removing device is fitted around the exposed portion of the bolt. The device is then pushed upwardly to raise the nut segments against the spring.

Abstract: Nut which is separated into segments so that the segments can be expanded or contracted being guided at a tapered hole formed in the nut segments, characterized in that a tapered hole has an inlet port at a narrower end and an insertion hole at a broader end so that a bolt to be fastened can penetrated therethrough; nut segments have guide pins at their back which are always urged by a spring toward the narrower side of the tapered hole, and an operation ring is rotatably fitted to the outer periphery of the main body, and the operation ring is provided with a cam part which, when the operation ring is turned, moves the guide pins toward the broader side of the tapered hole against the spring to keep the positions of the nut segments, or releases the guide pins so that the nut segments are restored to the narrower side of the tapered hole by the force of the spring.