Clamping device

A clamping device comprising a clamp main body, a gripping assembly that passes through a through hole in an upper end portion of the clamp main body and extends upwards and is capable of gripping an inner circumferential surface of a hole in a workpiece, a clamp rod that extends in a vertical direction and is engaged with the gripping assembly, a scraper made from rubber or synthetic resin that blocks an annular clearance on an outer circumferential surface of the gripping assembly and the clamp rod within the through hole, a drive means that drives the clamp rod forwards and backwards, wherein;

• the gripping assembly comprises one or a plurality of grip forming members positioned at an outer circumference of the clamp rod;
• the clamp rod comprises an intermediate rod section at an intermediate portion, and a tapered section at its upper end side portion that continues upwards from the intermediate rod section, that is formed so that its external diameter increases progressively upwards, and so that it is capable of driving the one or a plurality of grip forming members in a direction to increase their external diameter;
• the tapered section has one or a plurality of tapered flat surfaces that contact with a grip claw section or sections of the one or a plurality of grip forming members in a surface contacting manner, and one or more partial conical surfaces having radius increasing progressively upwards each of which is formed respectively between edges of lower portions of the one or a plurality of tapered flat surfaces;
• and
• in the vicinity of the scraper, the cross section of the one or a plurality of grip forming members and the clamp rod orthogonal to an axis of the clamp rod is formed as circular throughout an unclamping state to a clamping state.