Web infeed tension control system with dancer roll

A web infeed tension control system in a printing press for feeding a web of material from a paper feed roll to a printing plate roll driven at a predetermined speed by a drive motor, said system comprising;

• a web infeed roll, a differential drive unit drivingly connected with said web infeed roll, said differential drive unit including a circular spline, a flexible spline, and a wave generator with an output shaft thereof coupled to said web infeed roll;
• wherein a rotation input is imparted from said drive motor to said flexible spline while a portion of said input is imparted to said wave generator in the direction opposite to rotation of said flexible spline, and the result of computing two said rotation inputs is obtained from said circular spline to produce an output;
• said system further including a clutch means changing state of coupling between said differential drive unit and said drive motor in accordance with the result of computation;
• dancer roll mechanism interposed between said web infeed roll and a pinch roll, said dancer roll mechanism including a dancer roll pressed against said web material with a constant pressure, a lever arm, pivot means pivotally supporting the lever arm midway between its ends, means rotatably mounting the dancer roll to the lever arm at one side of its pivot, an air cylinder, means pivotally supporting the air cylinder at one end for pivotal movement, a piston in the air cylinder, a rod connecting the piston to the lever arm at the other side of its pivot, a control valve, a valve part in the control valve movable therein to open and close the control valve, transmission means connecting the valve part to the lever at said other side of its pivot and a solenoid valve connecting said air valve and control valve so as to provide communication therebetween, wherein said dancer roll is so adjusted as to be in an equilibrium of force to the tension of said web material by said air cylinder via said lever arm, and said control valve applies, in response to changes in the preset tension, a control pressure to said air cylinder for enabling the dancer roll to continue the action at a fixed position;
• a web tension sensor means positioned between said pinch roll and the printing plate roll for sensing tension changes in said web material;
• and control means computing signals of said web tension sensor means in a phase advance circuit and controlling the rotation speed of said wave generator via said clutch means.

A web infeed tension control system in a printing press for feeding a web of material from a paper feed roll to a printing plate roll driven at a predetermined speed by a drive motor, said system comprising;

• a web infeed roll, a differential drive unit drivingly connected with said web infeed roll, said differential drive unit including a circular spline, a flexible spline, and a wave generator with an output shaft thereof coupled to said web infeed roll;
• wherein a rotation input is imparted from said drive motor to said flexible spline while a portion of said input is imparted to said wave generator in the direction opposite to rotation of said flexible spline, and the result of computing said two rotation inputs is obtained from said circular spline to produce an output;
• said system further including a clutch means changing state of coupling between said wave generator and said drive motor in accordance with the result of computation;
• dancer roll mechanical interposed between said web infeed roll and a pinch roll, said dancer roll mechanism including a dancer roll pressed against said web material with a constant pressure, a cantilever-supported air spring, a solenoid valve and a lever arm coupling said dancer roll and air spring;
• wherein said dancer roll is so adjsuted as to be in equilibrium of force to the tension of said web material by said air spring via said lever arm to continue the action of said dancer roll at a fixed position;
• a web tension sensor means for sensing tension changes in said web material as it travels from the pinch roll to the printing plate roll, and control means computing signals of said web tension sensor means in a phase advance circuit and controlling the rotation speed of said wave generator via said clutch means.