Rotary viscosimeter

A rotary viscosimeter, comprising:

• a rotor which is driven to rotate while contacting with a liquid of which a viscosity is to be measured;
• a rotor shaft which supports the rotor and is a first drive shaft for transmitting a rotational drive force to the rotor;
• rotating drive means having a drive power source for driving the rotor to rotate and an input shaft for outputting the drive power;
• a second drive shaft for transmitting the drive power to the rotor shaft;
• a first linking means for elastically linking said output shaft with the second drive shaft via a spring for transmitting the drive power therebetween;
• support means having a pivot and a bearing for rotatably bearing and supporting the rotor shaft;
• and
• a second linking means which bypasses said support means for linking the rotor shaft with the second drive shaft,
• wherein said viscosimeter comprises rotational angular displacement detecting means for detecting a rotational angular displacement of said rotor shaft, viscosity calculating means for calculating said viscosity from the detected angular displacement, pivot protecting means having a locking mechanism for locking and unlocking the rotor shaft against and for rotating, respectively, a pivot separating mechanism for separating and contacting the pivot of said support means from and with the bearing, respectively, and
• control means for controlling said rotating drive means and said pivot protecting means,
• said pivot protecting means having a first state in which the rotor shaft is locked against rotating and the pivot of said support means is separated from the bearing and a second state in which the pivot of said support means is in contact with the bearing and locking of the rotor shaft is released;
• said control means having a control mode for measuring the viscosity by a spring relaxation method in which the control means controls the pivot protecting means so that the pivot protecting means is in the first and second state on starting and completion of measurement and in the second state during measurement and also controls said rotating drive means so that the torque on said spring of the first linking means reaches a preset desired value at the start of measurement.