Patent ID: 6901861

Claim:
An ink viscosity measuring device used in a printing apparatus that comprises: a printing cylinder ( 2 ), a pressing member ( 13 ), an ink roll ( 4 ), a wringing member ( 5 ) which faces said ink roll ( 4 ) in a tightly adhering manner and forms an ink collecting area (A) between said wringing member ( 5 ) and said ink roll ( 4 ), an ink circulation passage ( 10 , 12 ) which supplies ink to said ink collecting area (A) and recovers said ink, and an ink tank ( 8 ) which communicates with said ink circulation passage and functions as a supply source and recovery source for said ink; and in said printing apparatus, ink in said ink collecting area (A) is transferred to the printing cylinder ( 2 ) via said ink roll ( 4 ) and printed on sheets that pass between said printing cylinder ( 2 ) and said pressing member ( 13 ), wherein said ink viscosity measuring device comprises: a first rotating body ( 33 ) which is disposed inside said ink circulation passage ( 10 , 12 ) so that said rotating body can freely rotate; a second rotating body ( 29 ) which is disposed outside said ink circulation passage ( 10 , 12 ) and magnetically coupled to said first rotating body ( 33 ); an electrical driving means ( 22 ) which causes said second rotating body ( 29 ) to rotate, and imparts rotation to said first rotating body ( 33 ) that is magnetically coupled with said second rotating body ( 29 ); a load current value detection means ( 23 ) which detects changes in a load current value that occurs upon changes in a viscosity of ink that contacts said first rotating body ( 33 ) when rotation is imparted to said first rotating body ( 33 ) by way of passing an electric current through said electrical driving means ( 22 ); a memory means ( 151 ) which stores said load current values that correspond to respective changes in said viscosity value of said ink; and a calculating means ( 152 ) which compares respective load current values stored in said memory means ( 151 ) with said load current value detected by said load current value detection means ( 23 ), and calculates an ink viscosity value at the current point in time.